Cover Image
close this bookTraining Programme for Women Entrepreneurs in the Food-processing Industry - Volume II (UNIDO, 1985, 286 p.)
View the document(introduction...)
Open this folder and view contentsChapter 1 Dried Food
Open this folder and view contentsChapter 2 Vegetable Oil Extraction
Open this folder and view contentsChapter 3 Fruit and Vegetable Products
Open this folder and view contentsChapter 4 Cereal Products
Open this folder and view contentsChapter 5 Products from Pulses
Open this folder and view contentsChapter 6 Products from Root Crops
Open this folder and view contentsChapter 7 Nut Products
Open this folder and view contentsChapter 8 Meat Products
Open this folder and view contentsChapter 9 Fish Products
Open this folder and view contentsChapter 10 Dairy Products
Open this folder and view contentsChapter 11 Beverages

(introduction...)

Cover art work by Heidi Lange for the World Conference of the United Nations Decade for Women (Nairobi, Kenya, 1985).

This document has not been edited.

(introduction...)

PRODUCT/PROCESS DESCRIPTION

Drying is a process that removes most of the water from a food to give a long shelf life and/or to increase the convenience and value of the food. Different categories of dried foods can be identified -for example high volume low value crops such as staple cereals and low volume high value foods such as herbs and spices. The foods considered in this chapter are in the second category as these offer better opportunities to small scale processors.

PROCESS FLOW DIAGRAMS

1.1 Fruits and Vegetables

PROCESS

NOTES

Harvest

This should be done as carefully as possible to prevent spoilage, bruising and loss of quality during transport. Specially designed, low-cost boxes (Fig. 1) protect the food. It should not be piled on the ground or in vehicles.

Wash

Use clean water to remove stones, leaves, or soils.

Sort/grade

This is needed to produce a uniform dried product. Foods are sorted for colour, size, shape and maturity. Uniform size and maturity influence the drying time. Sorting is done by hand.

Peel

Peeling increases the rate of drying (because peel prevents moisture leaving the food). It is usually done by hand using sharp stainless steel knives, but small peeling machines are available for fruits (Fig. 2).

Cut/slice/core

Cut to reduce the size of pieces and allow faster blanching/sulphuring/drying. Usually by hand, small scale equipment available.

Pulp (for fruit leathers)

Small scale pulpers available. Pulp spread on polythene sheets for drying.

Blanch (for vegetables)

Blanch to destroy enzymes which would otherwise cause changes in colour, flavour and texture. (Starchy foods such as root crops are not blanched because gelatinised starch reduces the drying rate.)
The food is heated in hot water or steam for a short time (Table 3) and then cool (Fig. 3). Blanching also kills some, but not all, micro-organisms on the surface of the food. Care is needed to prevent blanched foods from being recontaminated before drying.

Acid dip/sulphur dioxide (optional for some fruits)

To reduce browning during drying. Dip in lemon juice or citric acid for 5-10 min. Treatment with sulphur dioxide by 1) sulphuring or 2) sulphite dip. Burning sulphur used at 350-400g/100kg fruit (or 2-3 tablespoons/kg fruit) in sulphuring cabinet (Fig 4). Exact amount depends on type of food, its moisture content and other pre-treatments used. Sulphite dip using 0.2-0.8% sodium or potassium metabisulphite solution. Neither should be used for red fruits as the colour is bleached. Care needed as sulphur dioxide causes coughing and eye irritation. Sulphite dip in open tanks or buckets. Sodium metabisulphite usually available from pharmacies.

Syrup pretreatment
(for crystallised/osmasol fruits)

Boil in 60-70% sugar for 10-15 min and then soak for up to 18 hours. Necessary for peels used in marmalade to prevent them floating. Up to half of the water in the fruit is removed and therefore increases production rate in the drier. Gives good colour retention in food and sweeter, blander product. However lower acid levels may lead to spoilage if the food is not properly dried and packaged.

Dry

Rate depends on temperature, humidity and speed of air, type of drier and size of food pieces. Generally herbs are dried at: 35-40°C, fruits and vegetables: 38-60°C, meat and fish: 60-66°C. See notes below.

Package and store

See notes below.

1.2 Meat and Fish

PROCESS

NOTES

Transport

Should be done as carefully as possible to prevent damage which would cause microbiological spoilage, and loss of quality.

Sort/grade

Sort for correct variety, appearance, texture and absence of spoilage or disease.

Clean/prepare

Fish is de-scaled, split, gutted, washed and opened flat or filleted before drying. This is done carefully without spilling the gut contents onto the flesh as this would heavily contaminate the fish with bacteria. This is usually done by hand using a sharp knife and clean water. Meat is skinned, jointed and sliced. Skinning/descaling increases the rate of drying because skin/peel prevents moisture leaving the food.

Salt

Fish and meat can be treated by a number of methods. Dry salt is rubbed into the flesh and placed in the drier. Alternatively layers of salt and fish (about 1kg salt per 2kg fish) are stacked, flesh-side up on slatted wooden racks for 1-2 weeks. Weights are put onto the pile to compress it. The fish is then washed to reduce the level of salt, wiped dry and placed in the drier. Meat and some fish can also be soaked in brine (e.g. 5% salt for 12 hours) wiped dry and placed in the drier. (NB. Salt may contain dust, sand and other mineral salts which contaminate the food. Care should be taken to ensure that food grade salt is used).

Dry

See notes below.

Pack and store

See notes below.

1.3 Herbs and Spices

PROCESS

NOTES

Harvest

Harvest when mature: for black pepper when the oldest berries are just turning yellow or red and are hard to the touch; cardamom when the ripe capsule has black seeds, chillie when it starts turning red.

Sort/clean

Remove dust, dirt and stones by hand using a winnowing basket, wash in clean water which is changed frequently (e.g. once every hour). Cardamom capsules are dipped in a solution of 4% sodium carbonate for 5-10 minutes and allowed to drain before drying.

Dry

Black pepper berries are dried in 3cm layers for 4-5 days to 8% moisture. Cardamom is dried to 8% moisture in the dark to retain the green colour of the capsules. A high humidity is maintained in the drier for 2 hours to inactivate enzymes that break down the chlorophyll, and then reduced. Chillie is dried to 10% moisture. Care is needed to prevent overdrying. Drying temperature is controlled below 50°C for pepper and cardamom and below 60°C for chillie to prevent loss of flavour components.

Grade/package/store

Chillie and cardamom are graded by colour and size; deep green colour and large capsules have higher grade for cardamom. For chillie, bright red colour has higher grade. Pepper is graded by size, colour and relative density. Machines are available to grade pepper by size or relative density but a trained person with a winnowing basket is preferred for small scale production. The optimal storage conditions are low temperature, low humidity and freedom from pests.

ADDITIONAL PROCESSING NOTES

Drying

The rate at which food dries depends mostly on the properties of the drying air. These are:

1) relative humidity (RH),
2) temperature and
3) air speed.

Temperature and relative humidity: Air contains water vapour and the amount of water carried by the air varies with its temperature. At higher temperatures the air can carry more water vapour than at lower temperatures, so to dry foods it is necessary to raise the air temperature and hence obtain a low RH.

Air speed: Faster moving air carries away moisture more quickly from the food and the food therefore dries faster than in slow moving or stationary air. The air speed is increased by fans or by heating the air.

During initial stages of drying, water is lost from the surface of the food and the drying rate is controlled by all three of the above factors. In later stages moisture moves from inside the food to the surface. Here the rate is mostly controlled by the temperature of the food. The air speed and relative humidity have a much smaller effect.

NB: Not all foods need a high rate of drying. Some, for example, fruits and meat undergo 'case-hardening', if the rate of drying is too high. When this happens a layer of sugar and minerals forms on the surface of the food and seals it. This forms a barrier which prevents further water from leaving the food. So the food has a tough skin and is wet inside. Further drying is not possible. To overcome this the rate of drying is reduced either by reducing the temperature or the speed of the air (for example by drying in the shade).

In both initial and later drying stages the size of the pieces is important. In the first stage smaller pieces have a greater surface area for water to evaporate from. In the second stage the smaller the pieces the less distance the moisture must move to reach the surface of the food (Fig. 5).

Scale of Operation of Driers

The smaller volume of low volume/high value products means that smaller driers can be used (compared for example to cereal crop driers) and the higher value of the products may justify the additional expense of the drier and fuel. The scale of operation is determined by the demand for the product and the drying rate for a particular food in a particular drier. In general 5-10 kg food will need a drying area of 1 m2. This will allow calculation of the size of the drier that is needed for a given weight of food per day when the above information is known. In general higher drying rates and better control over the drying conditions can be found with artificial driers. However there are advantages to sun and solar drying which are described below.

Sun and Solar Drying

To find out whether (and when) sun/solar drying is possible in the participants' communities the harvest times, food prices and weather patterns can be compared in that region using graphs (for example Fig. 6). Sun drying is traditionally done only in regions where in an average year the weather allows the food to be fully dried after harvest.

The main advantages of sun drying are the low capital and operating costs (because drying equipment and fuel are not used) and little expertise is required. The main problems with this method are as follows:

· theft or attack by insects, rodents and birds
· contamination with dust, dirt, dropping etc.
· no protection from rain
· slow or intermittent drying which increases the likelihood of spoilage
· relatively low quality products and variable quality due to over/under drying
· relatively high final moisture content and spoilage during storage
· large areas of land needed for the shallow layers of food
· laborious because the crop must be turned, moved if it rains, and
· animals must be kept away while drying takes place
· direct exposure to sunlight reduces the quality (colour and vitamin content) of some foods.

The quality of sun dried foods can be improved by the following methods:

· Sort, grade and clean the food
· Reduce the size of pieces
· Cover to prevent insect damage
· Shade if necessary to protect colour or flavour of food
· Protect from animals
· Cover for rain or dew at night

Solar drying has advantages over sun drying as follows:

They operate by raising the temperature of the air to between 10 and 30°C above normal air temperature. This makes the air move through the drier (Fig. 7) and also reduces its humidity. The higher temperature deters insects and the faster drying rate reduces the risk of spoilage by microorganisms. These factors improve the quality of the product. The higher drying rate also gives a higher throughput of food and hence a smaller drying area.

Food is enclosed in the drier and therefore protected from dust, insects, birds and animals. The driers are water-proof and the food does not therefore need to be moved when it rains, or at night to protect from dew. Finally, driers can be constructed from locally available materials at relatively low cost.

Situations where solar driers may be useful:

· where fuel/energy is expensive or erratic
· to supplement existing artificial driers and/or reduce fuel costs
· where land for sun drying is in short supply or expensive
· where sunshine is plentiful but humidity is high.

Situations where solar drying is not likely to be useful:

· where the quality of sun dried foods is acceptable

· where fuel is plentiful and cheap

· where the additional costs of a solar drier are not recovered from increased value of the food and there is no incentive for producers to risk higher amounts of money in a drier when there is not a greater return.

Other disadvantages of both solar (and artificial driers include greater space and labour requirements than traditional methods (for example loading, unloading of trays). They may require labour which is normally provided by children or mothers carrying babies in traditional methods. This is therefore additional work for women.

Available Designs of Drier

Designs vary from very simple direct solar driers (for example a box covered with plastic to trap the sun's heat) to more complex indirect designs which have separate heaters and drying chambers. In indirect designs solar radiation falls onto collectors which heat up air which is used to dry the food. The most common type of collector is a bare galvanised iron plate which is painted matt black. Glass covers are best but they break easily, are heavy and expensive. Plastic often has poor stability to sunlight and weather, but is about 10% of the weight of glass and does not break. The best types of plastic are polyester and polycarbonate when these are available. Polythene is cheaper and more widely available but is less strong and less resistant to damage by light and weather. It will need replacing about every six months.

Common designs include 1) tent driers (direct) (Fig. 8), 2) cabinet driers (direct or indirect) (Fig. 9) and 3) chimney driers (indirect) (Fig. 10). Each of these types uses natural air circulation (convection) although it is possible to fit an electric or wind powered fan to increase the speed of the air.

QUALITY CONTROL

Raw material control

Details of the quality characteristics used in grading and sorting are in the process flow diagrams.

Foods should be harvested at the correct stage of maturity. If they are overripe they are easily damaged and may be difficult to dry; underripe and they have a poor flavour, colour and appearance. The main characteristics of fruit, vegetables, meat, fish and spices are shown in Table 1.

Table 1: Quality Characteristics of Raw Materials

Food

Characteristic to be Examined


Variety

Appearance

Maturity

Size/shape

Colour

Texture

Freedom from infection

Fruits

·

·

·

·

some

·

·

Vegetables

·

·

·

·

some

·

·

Meat

·

·



·

·

·

Fish

·

·



·

·

Spices

·

·

·

·


some

·

All food should be prepared as soon as possible after harvest to minimise spoilage before drying begins. This is particularly so for wet low acid foods such as vegetables, meat, fish etc. which can support the growth of food poisoning bacteria. Strict hygiene is necessary at all stages to reduce the risk of food spoilage and food poisoning. This must include proper cleaning of tools, equipment and workrooms, washing hands, and removal of food wastes. Excepting vegetables that are blanched, any bacteria or moulds that contaminate the food before drying are likely to remain on the dried food because the temperature of drying is not high enough to kill them. Preparation procedures for foods from the three categories are summarised in Table 2 and production methods are shown in the flow diagrams.

Process control

The main control points are 1) uniform sized pieces of food, 2) correct preparation procedures, 3) correct drying conditions (air temperature, humidity and speed and amount of food loaded into the drier), 4) correct drying time. These will each vary according to the nature and size of the food, the type of drier, climate at different times of the year and the type(s) of preparation procedures used.

Table 2: Preparation procedures

grading

cleaning skinning

sorting/reduction

peeling/

size

blanching dioxide

salting

sulphur

Fruit

·

·

·

·

·

some

Vegetables

·

·

·

·

·

·

some

some

Meat

·

·

·

·

·

·

Fish

·

·

·

·

some

·

Herbs/spices

·

·

·

some

Product control

Table 3

Food

Blanching time (min) using


steam

water

Leafy vegetables, sliced beans

2-2.5

1.5

Squashes, cabbage

2.51

5-2

Peas

3

2

Carrots

3-3.5

3.5

Cauliflower

4-5

3-4

Potatoes

6-8

5-6

If products are dried correctly they should have an acceptable appearance, colour, texture, taste and microbiological quality. This is retained by adequate packaging and storage conditions for the expected shelf life. The main reason for loss of quality during storage is moisture pickup and this can be assessed by simple tests for dryness as follows:

FRUIT AND MEATS: A handful of fruit or meat when compressed should neither stick together nor leave any trace of moisture in the hand. It should feel leathery and flexible. Meat may be further dried to the point where it feels stiff.

VEGETABLES: Should feel flexible-leathery to brittle and generally drier than fruits. Pieces should fall apart after being squeezed together.

FISH: Should retain no imprint when squeezed between thumb and forefinger. It will feel either leathery or brittle.

HERBS AND SPICES: Crumble easily when rubbed together.

Other changes to selected foods during drying and storage are summarised in Table 4 together with summaries of the causes and correctiver actions.

Table 4 Quality Control Checks

Change

Example of food

Fault

Correction

Browning

Fruits and vegetables

Enzyme activity

Blanch for the correct time and temperature, reduce the size of pieces

Loss of flavour

All foods

Temperature too high, time of drying too long, poor packaging

Lower the temperature, use gas barrier packaging

Loss of colour

Carrot, pepper

Enzyme activity air and light

Blanch, reduce the drying time, store away from sunlight, use a light-proof package or use sulphur dioxide treatment

Case hardening

Fish, fruit

Drying rate too high

Reduce the drying rate, make the pieces smaller

Slow rehydration

Any food

Pieces too large poor drying conditions, case hardening

Make the pieces smaller, optimise the drying conditions

Loss of texture

Fish, vegetables fruit

Enzyme activity, poor drying conditions

Blanch, optimise the drying conditions

Shrinkage

All foods

Drying rate too high

Optimise drying conditions

Microbial

All foods

Food too moist after drying

Dry to a lower moisture content

PACKAGING AND STORAGE

The factors that cause spoilage of dried foods are:

· moisture
· heat
· air
· odours
· light
· crushing
· micro-organisms
· insects and rodents
· shelf life

The need for packaging of dried foods depends on the nature of the food. Some (for example grains and tea, dried fish and spices) are called non-hydroscopic foods and these do not absorb much water from the air during storage. As a result the food remains dry and micro-organisms cannot grow on it. It does not therefore spoil and simple packages (baskets, jute sacks, wood or cardboard boxes) are sufficient These foods should be stored correctly, away from heat, temperature fluctuations, rodent and birds. Beans and grains can also be protected from insects by using hot pepper or bay leaves in the container.

Other types of food (for example salt, sugar, dried fruit) are hygroscopic and are able to pick up water from the air. The higher water content then allows moulds and some types of bacteria to grow on the food, and as a result it spoils. The need for packaging is therefore different for different types of food. Those that are hygroscopic need packaging in ceramic or glass jars, tins or plastic films to exclude moisture.

Some types of dried food, particularly those that contain fats or fat-soluble vitamins are also spoiled by oxygen in the air. The packaging for these types of food should also therefore exclude air. Polythene is often used but it is not the best material. Other types of packaging such as cellulose or polyprolene films are better for longer storage but these are more expensive and often unobtainable. In practice polythene can be used if it is the correct food grade quality and the food is not stored for more than a few weeks. Unsuitable polythene will give off-flavours to the food and allows air to penetrate. All types of packaging should be properly sealed to exclude air, moisture and insects (for example plastic is heat sealed and not folded or stapled).

ADDITIONAL NOTES FOR OPTIONAL MATERIAL

Advantages and limitations of drying

· long shelf life

· reduced weight and bulk for transport and distribution costs,

· greater convenience - high local demand for some products

· preparation of raw materials for further processing (e.g. dried fruit for bakeries, herbs for soups etc.)

Limitations of dried foods

· loss of quality (vitamins, colour, flavour, and texture are all lower than in fresh foods)

· Some products are preferred fresh (e.g. vegetables, fruit and meat)

· Small amounts of some products are used (herbs, spices) and therefore a relatively small market.

If drying is not traditionally done in an area, it is usually because the climate is not suitable and the food does not dry fast enough, or does not dry to a low enough moisture content to prevent it becoming mouldy during drying or storage. If a drying project is to be introduced to such an area, it is usually because new foods are grown in that area (e.g. new high yielding varieties or wheat replacing rice as a staple), production of a particular crop is cheaper in the new area than in the traditional areas in which the food was previously grown, or a second crop may be grown and harvested out of the normal season.

In such cases, it is necessary to heat the air using fuel, electricity or solar energy. The food will also need more protection to stop moulds and other types of spoilage during storage. This may mean additional packaging or a more sophisticated type of storage. All of these inputs increase the cost of the process and hence the cost of the product. Before a project is started it is therefore necessary to accurately find the demand for the dried food and also the price that customers are willing to pay for it. In other words a market survey and full financial evaluation are necessary to make sure that the work will not cause additional costs to the farmer and/or that it will actually generate income.

Income Generation

A judgement on the economics of a drying process will include some of the following questions:

· Will the drier increase the processors' output for the same inputs (for example, by reducing losses of increasing drying rate)?

· If the costs increase to get a larger amount of dried foods, would the increased income cover the additional costs (i.e. will the processor find markets for the extra dried foods)?

· Would the use of a drier bring new opportunities for the processor (for example allowing the time saved to sell produce to other producers)?

Use these questions to produce a formula as follows:

Total costs = initial investment + maintainance + labour + cost of food + other expenses

Benefits = value of the food × weight dried in a given time + health benefits + other factors

Decide whether drying is economically viable on the basis of these costs and benefits and compare the economics of drying with other types of processing, for example, pickling, jam making (Is drying an economical option for the particular area?).

A number of different production systems can operate for income generation if there is a market for dried foods: for example small scale family drying for local sale, cooperative drying of grains or fish and service drying for local farmers or fishermen. It is unlikely that the quality of agricultural products such as grains and other staple crops will be suitable for an export market, but there may be opportunities for high value/lower volume products such as spices, enzymes, starches and other ingredients for food manufacturers.

Equipment

Drying

Peeling machine (Fig. 2)
Blancher (Fig. 3)
Sulphuring Cabinet (Fig. 4)
Drier (Fig. 8 - 12)

Further Reading

BOWREY, R.G., BUCKLE. K.A., HAMEY AND PAYENAYOTIN, P., (1980) Use of solar energy for banana drying drying I food technology in Australia, 32, 6, 290-291

BROOME, R.H., (1952) In the orchard - sun drying of apricots Journal of Agriculture (Victoria), December

BUELOW, F.H., (1961) Drying crops with solar heated air Proceedings of UN conference on New Sources of Energy, Rome, Italy. Rome: FAO

BUELOW, F.H., (1962) Corrugated heat collectors for crop drying Sun at work, 1962, 8-9

CHAKRABORTY, P.K., (1976) Solar drying for drying fish and fishery products Research and Industry 21, 3.192-194

CHAKRABORTY, P.K. (1978) Technological development in artificial and solar dehydration of fish in India. Proceedings of symposiom of fish utilisation technology and marketing in the IPFC region (IPFC/78/SYMP/31), Manila, Phillipines, Rome, Italy, FAO

CHEEMA, L.S., AND RIBERTO, C.M.C. (1978) Solar driers of cashew, banana and pineapple. Proceedings of ISES conference "The sun: mankind's future source of energy" pp2075-2079. New Dehli, India. Australia: ISIS 2184pp

CLARK, C.S., (1981) Solar food drying: A rural industry Renewable energy review journal 3,1,23-26

CLARK, C.S., (1982) A solar food drier for Bangladesh Appropriate Technology 8,4,14-16

CLARK, C.S. AND SAHA, H., (1982) Solar drying of paddy Renewable energy review journal, 4. 1, 60-65

CLUCAS, I.J., (1981) Fish handling, preservation and processing in the tropics, Part I Report G144, TDRI, London, UK, 144pp

DOE, P.E., (1979) A polythene tent fish drier - a progress report Proceedings of conference "Agricultural Engineering in National Development". Paper 79-12, Selangor, Malaysia. Selangor: University Pertanian.

DOE P.E., AHMED, M., MUSLEMUDDIN, M., AND SACHITHINANTHAN, K., (1977) A polythene tent drier for improved sun drying of fish Food Technology in Australia, 29,437-441

EXCELL, RHB AND KORNSAKOO, S., A low cost solar rice drier Appropriate technology, 5,1,23-24

EZEKWE, C.I., (1981) Crop drying with solar air heater in tropical Nigeria Proceedings of ISES solar world forum, Brighton, UK. LONDON; ISES

GOMEZ, M.I, (1982) Effect of drying on the nutritive value of foods in Kenya in Food Drying., IDRC-195e (Ed.) Yaciuk G. Ottawa, Canada: International Development Research Centre. 104 pp.

GRAINGER. W., OTHIENO, H., AND TWIDDLE, J.W., (1981) Small scale solar crop driers for tropical village use - theory and practical experience Proceedings of ISES Solar world forum, Brighton, UK. LONDON; ISES

HARIGOPAL, U., AND TONAPI. K.V., (1980) Technology for villages - solar drier India Food Packer, 34,2, 48-49

HOPE, G.W., AND VITALE, D.G., (1972) Osmotic dehydration - a cheap and simple method of preserving mangoes, bananas and plantains. Report IDRC 004 el. International Development Research Centre, Ottawa, Canada. 13pp

ISLAM, M.N., AND FLINK, JM., (1982) Dehydration of ptato. I - air and solar drying at low air velocities Journal of Food Technology, 17, 373-385

ISMAIL, M.S., LAH T.A.T. AND BUYONG, A.A., (1982) Solar drying of marine products Regional journal of energy, heat and mass transfer, 4, 1,59-70

JOHNSTOON, J.C, (1979) Solar roofs dry african crops Sunworld, 3,6,161 -163

KEENER, H.M., SABBAH, M.A., MEYER, G.E., AND ROLLER, W.L., (1977) Plastic film solar collectors for grain drying Journal article no 14-77, Ohio Agricultural Research and Development Centre, Wooster, USA, 21pp

KOK, R., AND KWENDAKWENA, N., (1983) The construction and testing of a solar food drier in Zambia Paper no 83-4538, ASAE, St. Joseph, USA, 14pp

LAWAND. T.A., (1966) A solar cabinet drier Solar Energy 10,4,158-164

McBEAN, M.G., JOSLYN, M.A., AND NURY, FS., (1970) Dehydrated Fruit Report, Commonwealth Scientific Industrial and Research Organization, Sydney, Australia

McDOWELL, J., (1973) Solar drying of crops and foods in humid tropical climates Report CFNI-T-7-73, Caribbean Food and Nutrition Institute, Kingston, Jamaica. 42pp

MENDOZA, E.R., (1979) Performance of a low cost solar crop drier Proceedings of inter-regional symposium on solar energy for development, paper B-7, Tokyo, Japan, TOKYO: JSETA

MAHWALI, M., (1966) The drying of yams with solar energy Technical report T27, Bravce Research Institute, Saint Anne de Bellevue, Canada. 17pp

OTHIENO, H. GRAINGER, W., AND TWIDDELL, I.W., (1981) Application of small scale solar crop driers to maize drying in Kenya. Proceedings of 2nd conference oon energy for rural and island communities. Inverness, UK. LONDON Pergamon Press

OZISIC, M.N., HUANG, B.K.. AND TOKSOY, M., (1980) Solar grain drying Solar energy, 24,397-401

PABLO, I.S., (1978) The practicality of solar drying of tropical fruits and arine products as income generation for rural development. Proceedings of UNESCO solar drying workshop, Manila, Phillipines. MANILA; BED

PATTERSON, G., AND PEREZ, P., (1981) Solar drying in the tropics Santa Monica, USA: Meals for millions/Freedom From Hunger Foundation. 13pp

PONTING, J.D., WAITERS, G.G., FORREY, R.R., AND STANLEY, W.L., (1966) Omotic dehydration of fruits. Journal of Food Technology, 1, 10, 125-128

PUIGGALI, J.R., AND VARICHON, B., (1982) First prototypes for small fruit and vegetable country solar driers (in) Drying '82, (ed) Majumdar, A.S., LONDON, UK, Hemisphere Publishing Corp.

RAHMAN, R.K., (1981) Solar drying technoloogy for fruits and vegetable preservation Bangladesh Quarterly, 2,1,7-10

SHAW, R., (1981) Solar drying potatoes Appropriate Technology, 7, 4, 26-27

SINGH, H AND ALAM, A., (1981) Solar cabinet drier for chilli drying seeds and farms, VII, 7,25-26, 31

TRIM, D.S. K.O. H.Y., (1982) Development of a forced convection solar drier for red peppers Tropical Agriculture (Trinidad) 49,4,319-323

VOIROL, F., (1972) The blanching of vegetables and fruit Food Process Industries, August

WAGNER, C.J., COLEMAN, R.L., AND BERRY, R.E., (1980) Pretreatment for solar and hot-air drying. Proceedings of Florida Horticultural Society, 93,336-338

WATERMAN, JJ. (1976) The production of dried fish Fisheries Technical Paper 160. FAO, Rome, Italy, 52pp

WHILLIER, A., (1964) Black Painted solar air heater of conventional design Solar Energyu, 8,1, 31-37

WILHEIM, W.G., (1980) Low-cost solar collectors using thin-film plastic absorbers and glazing Proceedings of 1980 Annual Meeting of American Section ISES, Phoenix, USA, New York: ISES


Figure 1 BOX FOR USE IN HARVESTING


Figure 2 PEELING MACHINE FOR FRUITS


Figure 3 BLANCHING OF VEGETABLES


Figure 4 SULPHUR CABINET


Figure 5 SURFACE AREA OF PIECES TO BE DRIED


Figure 6 TO FIND OUT WHETHER SUN/SOLAR DRYING IS POSSIBLE IN A REGION


Figure 7 SOLAR DRYING


Figure 8 SOLAR TENT DRIER


Figure 9 CABINET DRIER


Figure 10 SOLAR MAIZE DRIER (CHIMNEY DRIER)


Figure 11 CABINET DRIER


Figure 12 PHILIPPINE MOBILE CABINET-TYPE MULTI-TRAY SOLAR DRIER

(introduction...)

PRODUCT/PROCESS DESCRIPTION

Edible oil is a valuable product that has universal demand for domestic use, as an ingredient for other local food production (for example bakeries and fried snackfoods), as a raw material for industrial use and as an export commodity (for food use, as body/hair oil and detergents). A major non-food use for oil is in soapmaking. Uses for different oils are summarised in Table 1.

Principles of Preservation and Methods of Processing

The principles of preservation are 1) to destroy enzymes in the raw material and contaminating microorganisms by heat during processing and 2) to remove as much water from the oil as possible to prevent microbial growth during storage. Oil therefore has a long shelf life due to its low moisture content. Proper packaging and storage conditions are needed to slow down chemical deterioration (rancidity).

The method used for processing depends on the type of raw material available. Raw materials can be grouped according to the part of the plant that contains the oil or fat (Table 1). The main difference in raw materials is the moisture content. Raw materials with a low moisture content include seeds and beans which are dried on harvest and some nuts. Coconuts are usually dried (to copra), but palm fruits, olive fruits and sometimes coconut are processed wet.

Only seeds, nuts and fruits that contain considerable amounts of edible oil are used for small scale oil extraction. Other types (for example maize) may contain edible oil but the quantities are too small for economic processing on a small scale. However not all oil-rich seeds and fruits have edible oil. Some contain toxins or unpleasant flavours and these are only used for varnishes, paints etc. and are not eaten. Others (for example castor oil) need very careful processing to make them safe for use as medicines. These are not suitable for small scale production.

PROCESS FLOW DIAGRAMS

2.1 Oilseeds

(sunflower, safflower, mustard, sesame)

PROCESS

NOTES

Dried seeds

Store

Store in weatherproof, ventilated room, on pallets to keep sacks off the floor. Protect against insects rodents and birds (Fig. 9).

Clean > soils

Sieve to remove sand, stones that would damage equipment, remove leaves etc. by hand

Decorticate

Small machines available (Fig. 1).

Winnow > husk

Small machines available (Fig. 2).

Heat condition

Not used for mustard/sesame to protect flavour of oil. Others should have moisture content 7-10% and temperature 80-90°C. Skill needed to condition correctly. Seed scorchers (Fig. 3) available.

Press/expell

Pressing 15-20 kg in 20-60 mins (Fig. 4). Expeller 20-50 kg/hour (Fig. 5).

Clarify

Small clarifier available (Fig. 6).

Package

Pack in lightproof, airtight containers.

Store

Store away from heat, sunlight etc., shelf life 2-12 months expected depending on packaging and storage conditions.

2.2 Groundnut/Palm Kernel

PROCESS

NOTES

Dried nuts

Store

Store in weatherproof, ventilated room, on pallets to keep sacks off the floor. Protect against insects rodents and birds (Fig. 9).

Decorticate/crack

Groundnut decorticators can be manual (Fig. 7) or powered. Palm kernels cracked in motorised hammer mill (termed a kernel cracker).

Grind

Rollers are used for groundnuts, hammer mill for palm kernels. Size of pieces reduced to 6-10 mm for both

Heat condition

Nuts should have moisture content 7-10% and temperature 80°C-90°C. Skill needed to condition correctly.

Press/expell

Pressing 15-20 kg in 20-60 mins (Fig. 4). Expeller 20-50 kg/hour (Fig. 5).

Clarify

Small clarifier available (Fig 6).

Package

Pack in lightproof, airtight containers.

Store

Store away from heat, sunlight etc., shelf life 2-12 months expected depending on packaging and storage conditions.

2.3 Coconut

PROCESS

NOTES

Dehusk

This is faster by skilled workers (3-4 nuts per minute).

Crack

Crack manually, water can be saved for vinegar production.

Shell

Pieces of coconut meat dried (copra) for later oil extraction, grind before use to 6-10 mm pieces or meat shredded using reamer (Fig. 8) for immediate use.

Press

Press 15-20 kg in 20-60 mins. (Fig. 4) Emulsion (or 'milk') extracted. Expeller may be used for copra.

Heat

Heat to 80-90° C to break the emulsion.

Skim oil Clarify

Small clarifier available (Fig. 6).

Package

Pack in lightproof, airtight containers.

Store

Store away from heat, sunlight etc., shelf life 2-12 months expected depending on packaging and storage conditions.

2.4 Palm Fruit

PROCESS

NOTES

Strip

Remove fruit from bunches, manually operated machine available.

Pulp

Pulp manually with pestle and mortar or more quickly with motorised pulper.

Press

Press 15-20 kg in 20-60 mins. (Fig. 4) Emulsion extracted.

Heat

Heat to 80-90° C to break emulsion.

Skim oil

Small clarifier available (Fig. 6) Clarify.

Package

Pack in lightproof, airtight containers.

Store

Store away from heat, sunlight etc., shelf life 2-12 months expected depending on packaging and storage conditions.

ADDITIONAL PROCESSING NOTES

Dehusking/decorticating

Some raw materials (for example groundnuts, sunflower seed) require decorticating and winnowing. The husk is removed because if left on it 1) has no value as animal feed, 2) it absorbs oil and 3) it increases the weight of material to be transported and processed. However in groundnut processing some fibrous material is needed. It allows the oil to escape from the press or expeller, and also prevents the nuts turning into peanut butter without releasing the oil. Some husk (about 10%) is therefore added back to the nuts to increase the yield of oil. However too much husk reduces the value of the oil cake as human food. Skill is therefore needed to judge the balance between the amount of husk needed for proper processing and the amount which reduces the value of the oilcake.

Oil extraction from dry crops

In all raw materials the oil is contained in oil bearing cells which must be ruptured to release the oil. The best way of rupturing the cells depends on the structure of the food. In some (for example groundnuts, dried coconut, palm fruit) pressure applied in a press is sufficient, whereas in others (for example avocado, oilseeds) a rubbing or "shearing" action is also needed. Traditional methods rely on pounding and sqeezing manually but this is time consuming and hard work. The output is not usually enough for income generation and the oil quality is very variable. Improved equipment for extraction of oil falls into two categories: presses, which only apply pressure and screw expellers which apply both pressure and a shearing action. A third method, used in large scale extraction, uses a solvent to dissolve the oil, but is not suitable for small scale operation due to 1) the high capital costs of equipment, 2) the need for solvents which may not be easily available and 3) the risk of fire or explosions.

Pressing

There are a large number of different types of presses but the principle of operation is similar for each. A batch of raw material is placed in a heavy metal "cage" and a metal plunger is used to press the material. The main differences in design are as follows: 1) the method used to move the plunger 2) the amount of pressure in the press, 3) the size of the cage. The plunger can be moved manually or by a motor. The motorised method is faster but more expensive. Different designs use either a screw thread or a hydraulic system (for example a lorry jack) to move the plunger. Higher pressures can be obtained using the hydraulic system, but care is needed to make sure poisonous hydraulic fluid does not contact the oil or raw material. Hydraulic fluid can absorb moisture from the air and lose its effectiveness, and jacks also wear out and need frequent replacement Screw threads are made from hard steel and held by softer steel nuts so that the nuts wear more quickly than the screw. These are easier and cheaper to replace than the screw. The size of the cage varies from approximately 5 kg - 30 kg with an average size of 15 kg. The pressure should be increased gradually to allow time for the oil to escape. If the depth of the raw material is too great, oil will be trapped in the centre. To prevent this, heavy "layer Plates" can be inserted in the raw material. The production rate of presses depends on the size of the cage and the time needed to fill, press and empty each batch. Hydraulic presses are faster than screw types and powered presses are faster the manual types. Some types of manual press require a considerable effort to operate.

Expellers

A rotating screw pulls the raw material from a hopper into the barrel where the seed is broken and pressure is gradually increased as it moves through the barrel. Oil passes through narrow slots in the barrel and press cake is discharged from the end through a 'choke' ring. This ring is adjustable to control the pressure in the barrel. The screw rotates at about 100 rpm and heat is generated due to friction between the seeds and the screw/barrel. Some designs have additional electric heaters around the barrel. The screw, choke ring and barrel all wear and must be repaired and replaced at intervals. There must therefore be mechanical skills available locally to carry out the maintainence and repair work. Sand or grit in the raw material reduces the time between repairs from several months to as little as two weeks and proper cleaning of the raw material is therefore essential.

Oil extraction from wet crops

Palm fruit is reruced to a fine pulp and the oil emulsion is pressed out. The remaining fibre is washed and the water added to the emulsion. The liquid is then heated to break the emulsion and the separated oil is skimmed off.

Clarification

Crude oil from both wet and dry crops contains a suspension of fine pulp and fibre from the plant material with small quantities of water, resins, colours and bacteria which make it darker and opaque. These contaminants are removed by clarifying the oil, either by allowing it to stand undisturbed for a few days and removing the upper layer, or by using a clarifier. If the oil is still not sufficiently clear for the consumer's requirements, it can be filtered through a plastic funnel fitted with a fine filter cloth. Finally the oil is heated to boil off traces of water and destroy bacteria. When these impurities are removed the shelf life of oils can be extended from a few days to several months, provided proper storage conditions are used.

Refining of oil

Oil from large scale production is further refined by degumming (removing dissolved proteins and other plant materials), neutralising fatty acids and bleaching any colours in the oil. This is rarely necessary for small scale producers who are supplying domestic customers, but one or more of these stages may be necessary for export markets. The correct control of these stages (particularly neutralisation) requires more complex chemical determinations and analytical equipment than is likely to be available for small scale producers.

QUALITY CONTROL

Hygiene

The heat treatment during processing and low water content of oil reduces the risk of bacterial food poisoning almost completely. The most important risk is from a mould that can grow on nuts or seeds that are not fully dried, which produces a poison called 'aflatoxin'. This is a highly dangerous poison and all precautions should be taken to dry raw materials properly and keep them dry before use. This is a particular problem with groundnuts and these should be shelled before storage to prevent mould growth beneath the shell.

Raw material control

Crops should be harvested when fully mature, as they then contain most oil and it is easily removed. Under-ripe materials give a lower yield of oil and are more difficult to process. Over-ripe fruits are easily bruised and this allows enzyme action and bacterial growth which reduces the oil yield and causes rancidity. Maturity is judged with experience, by the colour/size of the raw materials. Raw materials must be in prime condition because any deterioration leads to a rancid, unpleasant flavour in the oil. Oilseeds, copra etc. that are dried and stored before processing should be stored in weatherproof, ventilated rooms (Fig. 9) and should be protected against insects, rodents and birds. They should be fully dried before storage as inadequate drying and/or poor storage conditions allow mould growth. This causes spoilage which reduces the oil yield and may affect the oil flavour and colour in addition to the risks from aflatoxin.

Seeds and nuts in particular should be cleaned using a screen or sieve to remove soil, sand and grit which would rapidly wear out equipment Leaves, stalks, seeds from other plants and stones should be picked out

Process control

The main quality control point is conditioning of the raw materials by heating with small amounts of water. The degree of conditioning is critical. If the temperature is too high the material dries out, if it is too moist the oil yield is reduced. In practice the raw material should not be sticky (too wet) but also should not fall apart easily (too dry). The correct moisture content can be found by experience or by analytical determination. In addition gentle pressure should be applied to allow the oil to escape. Measurement of the oil yield is routinely made (% oil from raw material - see Table 1).

Product control

The main quality factors for oil are colour, clarity, taste/flavour and odour. Correct colour and clarity are mainly due to proper clarification after the oil has been extracted. The taste and odour of oil result from the type of raw material used and the extent of rancidity. The crude oil produced on a small scale is not usually refined to remove flavour and colour.

Table 1: Raw materials for edible oil production

RAW MATERIAL

Moisture
content (%)

Oil/Fat
content (%)

Yield
(% from oilseed)

Uses for
oil

Byproducts

Seeds and beans

Cotton

5

15-25

-

cooking soap

animal feed

Rape

6

40-45

25

cooking

animal feed (needs detoxifying)

Mustard

7

25-45

-

cooking

Sesame

5

25-50

45

cooking

animal feed

Sunflower

5

25-50

20-30*

cooking

(hulls used for chicken litter, presscake for animal feed)

Safflower seed

5

30

-

cooking

animal feed

Nuts

Coconut fresh

40-50

35-40

55-62

cooking

Copra

3-4.5

64-70

skin cream

Groundnut

4

28-55

40*

cooking

Shelled

4

6-57

45-49

soap

food (snacks, soup) animal feed

Palm kernal nuts

-

46-57

47-51

cooking, skin cream

animal feed

Shea nut

-

34-44

15-45*

soap cooking

fuel (shells) fuel

Fruits

Oil Palm

-

56

11-20

cooking

fuel

Avocado

69

11-28

40-44

skin cream

cooking

Olive

50-70

25

-

cooking, skin cream

animal feed fuel

* Traditional methods

PACKAGING AND STORAGE

Rancidity during storage is reduced by using clean, dry containers, excluding light and heat and avoiding contact with metals.

The main factors that cause rancidity during storage are

1) oxidadve rancidity, which takes place in air and is accelerated by light, the presence of copper and iron from machinery/containers and by high temperatures. Oil should be stored away from heat or sunlight, in a lightproof and airtight container which is filled to the top, and does not have iron or copper on the inner surface.

2) hydrolytic rancidity is caused by enzymes present in the raw materials or produced by contaminating bacteria. Bacteria grow on the oil if moisture, plant material or dust are present. The enzymes increase the levels of fatty acids and cause rancidity. This can be prevented by filtering the oil after extraction, heating oil to remove moisture and destroy enzymes and bacteria, and preventing moisture pickup during storage by using moisture proof containers.

Packaging

In view of the factors that cause rancidity described above, and the need to contain the oil without leakage, suitable storage containers include sealed glass or plastic bottles, preferably made from coloured glass or kept in a dark box, metal oil cans, where the metal is tin coated (to prevent oil from reaching the iron of the can), or glazed ceramic pots, sealed with a cork and wax stopper. Great care should be taken to properly clean oil containers if they are to be reused. A film of old, rancid oil on the inside of an empty container will quickly make fresh oil go rancid. The containers should be properly dried after cleaning to remove all traces of moisture. If correct storage conditions are not used the shelf life of the oil is reduced from many months to as little as a few days or weeks. Oilcake should be dried to prevent mould growth and stored in a cool dark place to prevent rancidity of oil remaining in the cake. It should be protected from insect and rodent attack using the same methods as those used for the raw material.

ADDITIONAL NOTES ON PRODUCTION ECONOMICS AND MARKETING

Oilseeds have a long storage life if sufficiently dry and oil processing can therefore continue throughout the year, thus making better use of equipment (compared to more seasonal products). The low volume of oil makes transport and distribution easier and distribution to a wider area also creates a larger potential market Producers can therefore receive an income throughout the year.

Byproducts contain protein and residual oil and are valuable as animal or human food (Table 1). Byproducts also have a long shelf life if properly dried and this allows income generation throughout the year. The potential income from oil extraction is often high enough to justify the relatively high costs of setting up and operating a production unit.

Potential disadvantages to oil extraction include the higher value of oilseeds compared to other crops and hence the higher financial risk from losses, the need for fuel, and the time-consuming and hard work. Equipment is relatively expensive and year-round production needs a large working capital to buy and store seasonal crops. There is also the risk of competition from large scale producers who are able to market high quality oils at a lower cost because of economies of scale.

Small scale extraction processes usually produce crude oil which has a different appearance and flavour to commercially refined oil. It is therefore essential that market surveys for consumer acceptability are conducted before production starts. Other considerations to running a smale scale oil extraction project include

1) The local demand for vegetable oils,

2) Sufficient raw material in the area for year-round work and adequate transport and storage facilities,

3) The relative prices of raw materials, crude oil, and oilcake to ensure profitability,

4) Availability and cost of materials and equipment,

5) Organisational/marketing skills available.

Equipment

· Sieve/screen 1-2mm mesh
· Decorticator (Fig 7)
· Winnower
· Heat conditioning pan or seed scorcher (Fig 3)
· Press (Figs 4, 4a) or Expeller (Fig 5, 5a & 5c)
· Clarifier (Fig 6)
· Bottle filler and sealer or film sealer
· Nut cracker
· Coconut scraper (Fig 8)
· Palm fruit bunch stripper
· Pulper
· Storage facilities (Fig 9)

Further Reading

Oil processing

GATE Oil presses: an introduction (GATE/GTZ Publications, Eschborn, Germany, 1979)

UNIDO Appropriate industrial technology for oils and fats (United Nations, New York, 1979)

UNIDO Guidelines for the establishment and operation of vegetable oil factories (United Nations, New York, 1977)

CORBETT, S A new oil press design: but is it any better? VITA News, (Vita Pubs, Washington DC, 1981)

RAO, P.V.S. A study of village oil industry in India (Appropriate Technology Development Association, Lucknow, 1980)

BOYD, JOHN A buyer's guide to low-cost agricultural implements (Intermediate Technology Publications Ltd., London, 1976)

GODIN, V.G., and SPENSLEY, PC. Oil and Oilseeds, Crop and Product Digests No. 1 (TPI, London, 1971)

German Adult Education. Make your own oil. Association Africa Bureau, Ghana, (traditional palm oil processing)

NWANZE, S.C., The hydraulic hand press. Nigerian Institute for oilpalm research, 4 (15), (1985)

HARTLEY, C.W.S., and NWANZE, S.C. Factors responsible for the production of poor quality oil. The Oil Palm, pp 68-72. (Tropical Products Institute, London 167 pp., 1965)

ACHAYA, K.T. Appropriate technology for production and processing oils and fats. Paper presented at International Forum of Appropriate Industrial Technology (UNIDO, New Delhi, 1978).

SRIKANTA RAO, P.V, A search for appropriate technology for the village oil industry (ATDA Pubs. Lucknow, India, 1978)

TPI Oil and oilseeds. Crop and Product Digests, No 1, London, (1971) Palm oil TPI Processing of oil palm fruit and its products (TPI Pubs, London, 1973) BLAAK, G.A village palm oil mill. Oil palm news, 23,5-11, (1979)

CORNELIUS, J.A. Processing of oil palm fruit and its products (London: Tropical Products Institute, 95pp, 1983)

KING-AKERELE, 0. Traditional palm oil processing, women's role and the application of appropriate technology (United Nations Economic Commission for Africa 1983 ST/ECA/ATRCW/82/02, 1983)

COWARD, L.D.G. Assistance in the design of a prototype palm oil extraction press for rural areas SI/CMR/82/801 Cameroon (UNIDO. Vienna, 1985)

ATA, J.K.B.A. Processing and quality characteristics of Ghanaian commercial palm oils Ghana Journal of Agricultural Science, 7(2), 147-149, (1974) BERGER, K. Production of palm oil from fruit. Journal of the American Oil Chemists' Society, 60, 158A - 162A, (1983)

CORNELIUS, J.A. International standards for palm oil. Journal of the American Oil Chemists' Society, 54943A-948A, (1977)

COURSEY, D.G. The deterioration of palm oil during storage. Journal of the West African Science Association 7(2), 101-115, (1963)

HARTLEY, C.W.S. The oil palm (2nd Ed. Longmans, London, 806 pp, 1977)

JOHNSON, R.M. and Elaeis RAYMOND, W.D. The African oil palm, guineensis. Colonial Plant and Animal Products, 4(1), 14-23, (1954)

JACOBI, C. Palm oil processing with simple presses GATE Magazine (GATE/GTZ, Eschborn, Germany, 1983)

MACLELLAN, M. Palm oil Journal of the American Oil Chemists' Society, 60, 320A - 325A, (1983)

DONKOR, P.A hand-operated screw press for extracting palm oil. Appropriate Technology vol 5, No 4. (1979)

NWANZE, S.C. Semi-commercial scale palm oil processing. The Oil Palm, pp 63- 66. (Tropical Products Institute, London 167 pp., 1965)

RUTOWSKII, A. Traditional palm oil processing in Western Africa. Fette Seifen Anstrichmittel, 85 (7), 262-267., (1983)

TCC Extraction of palm oil using appropriate technology hand screw press. (Technology Consultancy Centre Report, Ghana, 1978)

BOWEN, B.H.A screw press for low cost palm oil extraction. Engineering Research Publications Research Paper No TE12, (Univ of Sierra Leone, Freetown, Sierra Leone, 1976)

Coconut

ATEN, A., MANNI, M., and COOKE, F.D. Copra processing in rural industries. FAO Agricultural Development Paper, No. 63 (FAO, Rome, 1958)

GRIMWOOD, B.E. Coconut palm products (FAO, Rome, 1976)

HAGENMAIER, Robert D Coconut aqueous processing (San Carlos Publications, Cebu City, Philippines, 1980)

THEIME, J.G. Coconut oil processing (FAO, Rome, 1968)

TPI Development of a wet coconut process designed to extract protein and oil from fresh coconut. (TPI, London, 1973)

ILO Small scale oil extraction from groundnuts and copra. (ILO Pubs, Geneva, 1983)

BANGOR, J., and and VELASCO, J.R. Coconut production utilisation. Philippine Coconut Research and Development Foundation Centre, (PCRDF), Amber Avenue, Pasig, Metro Manila, Philippines.

Oilseeds

HAMMONDS, T.W. HARRIS, R.V., MACCFARLANE, N. The small-scale expelling, of sunflower seed oil in Zambia. Appropriate Technology Journal, vol 12, No 1. (IT Pubs, London)

NIESS, T. New shea-butter technology for West African women. GATE Magazine GATE/GTZ Pubs, Eschborn, Germany, 1983)

BULK, J.V.D. UNATA Press No. 4, Heuvelstraat, 131,3140 Ramsel, Belgium, (1986)

TPI Rural Technology Guide 10 A hand-operated disc mill for decorticating sunflower seed. (TPI Pubs, London 1981)

TPI Rural Technology Guide 9 A hand-operated disc mill for decorticating sunflower seed. (TPI Pubs, London, 1981)

TPI An economic study of lauric oilseed processing (TPI Pubs, London, 1973)


Figure 1 DECORTICATER


Figure 2 COATED TROPIC RESISTANT PLYWOOD


Figure 3 SEED SCORCHER


Figure 4 OIL PRESS SHOWING LAYER PLATES


Figure 5 EXPELLER


Figure 6 CLARIFIER


Figure 7 GROUNDNUT DECORTICATOR


Figure 8 COCONUT GRATER


Figure 9 STORAGE

(introduction...)

PRODUCT/PROCESS DESCRIPTION

Types of Fruit Products

Drinks

All drinks contain pulped fruit or juice from a single fruit or a mixture of fruits. They can be divided into those that are drunk immediately after opening and those which are stored and used gradually. The first group should not contain any preservative but the second group need preservatives to have a long shelf life after opening. Unopened bottles of both types should have a shelf life of 3-9 months, depending on the storage conditions. Different types include:

i) Fruit juice (with nothing added).

ii) Nectars (which contain at least 30% fruit pulp and are drunk immediately after opening).

iii) Squashes (which contain at least 25% fruit pulp mixed with sugar syrup). They are diluted to taste with water and contain preservatives.

iv) Cordials (crystal clear squashes).

v) Syrups (which are boiled, filtered juices with a sugar content of 50-70%). They are used in the concentrated form and do not usually contain preservatives.

Fermented Juices

These include a range of fruit wines, vinegars and spirits. Yeasts ferment sugars in the juice to alcohol, which together with the natural acidity preserves the products when the concentration is high enough (more than 6% alcohol). Some low alcohol drinks are pasteurised to prevent spoilage. Vinegars are produced by a two-stage fermentation - first by yeast to produce wine and then by acetic acid bacteria to produce vinegar (acetic acid). Vinegars are normally standardised at 6-10% acetic acid, which preserves them from spoilage.

Fruits in Syrup

Fruits are packed into jars with a 30-50% sugar syrup. The filled jars are pasteurised and then sealed tightly while hot so that an internal vacuum forms when they are cool. Preservation depends on an adequate heat treatment and air tight (or "hermetic") seals.

Preserves (jams, jellies and marmalade)

Preservation depends on a high sugar content (68-72%) combined with the acidity of the fruit to prevent spoilage. The setting qualities and strength of the gel depend on the sugar content, the fruit content, the acidity and the amount of pectin (an extract from fruit skins) added. A careful balance is needed between the sugar, acid, pectin and fruit to achieve a good quality product. Jellies are clear filtered gels. Marmalades, which are generally made from citrus fruits, are gels which contain shreds of peel. Jams can contain whole fruit pieces, juice or fruit pulp.

Confectionary Products

Fruit cheese (e.g. guava cheese) is a jam type mixture that is further boiled to give a sugar content of 75-85%. It sets as a solid block. The high sugar level combined with the natural acidity prevents spoilage.

Dried Fruit Products

These include dried fruit pieces, fruit leathers and osmo-sol dried fruit. They are described in detail in the drying chapter. In general fruit products do not form a staple part of the diet but add variety and choice to staple foods. They are low cost raw materials, which are usually widely available in rural areas and different types are available throughout the year. Many of the methods of processing are relatively low cost and simple to use at a small scale and a wide variety of products are possible. Finally valuable extracts such as pectin or citrus oil may be produced as ingredients for other large scale manufacturers. However fruits (and vegetables) are bulky raw materials and incur high transport costs. In addition markets can be a long way from the growing areas which increases transport costs for what are relatively low value products. A demand for the products may not exist as people may prefer to eat fresh foods and do not worry if the food is not available for a short season each year. This is especially so if there is an alternative fruit or vegetable for them to eat. Do not attempt to use a surplus simply because it exists - the demand for the products must be demonstrated.

Types of Vegetable Products

Dry Salted Vegetables

The high salt concentration preserves the food by both drawing out water from the food and by the anti-microbial properties of the salt. Salt also interferes with the action of enzymes. Vegetables must be washed to lower the salt concentration before they are eaten. Dry salting does not need fuel, is simple to do and the food quality is well retained.

Brined Vegetables

A solution of salt (brine) is used to preserve vegetables. There are many different types of brine containing 2-16% salt, often with added sugar. However, higher concentrations require the vegetables to be washed before use. Those which have lower concentrations of salt may also be pasteurised to aid preservation.

Pickles and Sauces

Vegetables (for example cucumber, cabbage, olive, and onion), are fermented by lactic acid bacteria which can grow in low concentrations of salt. The bacteria ferment sugars in the food to lactic acid. In vegetable products the lactic acid then prevents the growth of food poisoning bacteria and moulds or other spoilage micro-organisms. The amount of added salt controls the type and rate of fermentation. If 2-5% salt is used a natural sequence of different bacteria produce the lactic acid. If higher concentrations of salt (up to 16%) are used, a different product called 'salt stock' pickle is produced. Sometimes, sugar is added to increase the rate of fermentation or to make the product sweeter. (The different types of pickles are shown in Table 1.)

Table 1: Types of Pickled Vegetables

Salt stock Pickle

Sweet Pickle

Sour Pickle

Brined Vegetables

Sauce

% salt

6-10%
for 10 days
then 16%

5

5

2-5

2-5

% sugar

-

2-15

-

2-5

to taste

Final product

3% salt
5% vinegar
2-10% sugar

3% salt
5% vinegar

3% salt
5% vinegar

3% salt
5% vinegar
2-5% sugar

various
salt, vinegar
+ sugar

Alternatively vinegar, salt and sometimes sugar are used to acidify vegetables and produce a variety of products but because the vegetables are not fermented they have a different flavour and texture. Sweet pickles and sauces are made from single fruits or mixtures of fruits and vegetables. They are preserved by the combined action of acetic acid, sugar and in some cases, added spices.

Dry vegetables (These are discussed in detail in Chapter 1 Dried Foods)

In general many vegetables have a longer harvest season and a longer shelf life in the raw state than fruits, and production can therefore continue for a larger part of the year. Many vegetables form the staple food in the diet or are used in soups and stews and they therefore have high demand. Some extracted products (e.g. sugar and starch) are valuable staples, which also have a high demand. In general vegetable processing is more difficult on a small scale than fruit processing because of the low acidity and hence the risk of food poisoning.

Most fruit products are acidic and are not spoiled by bacteria. They do not therefore carry the risk of food poisoning. Spoilage is by yeasts or moulds. Most vegetables are less acidic and are spoiled by bacteria and moulds. Some of these bacterial can cause food poisoning. In addition naturally occurring enzymes rapidly change the colour, flavour and texture of fruits and vegetables after harvest. These factors produce a characteristically short shelf life and rapid processing after harvest is therefore necessary. Preservation is achieved by either destroying enzymes and micro-organisms using heat (blanching, pasteurisation), or preventing their action by:

1) removing water (drying, boiling to make concentrated syrups or jam, using concentrated solutions of salt or sugar to draw out water from the food),

2) by increased acidity or chemical preservatives (acidity can be changed by adding acids (for example lemon juice or vinegar), or by fermentation. Examples of preservatives include sulphur dioxide and sodium benzoate).

3) by using low temperatures (freezing, chilling or cooling).

In this Chapter the use of low temperatures is not considered due to the high capital costs of equipment and the need for refrigerated distribution and storage. Canned fruit products are produced in a similar way to the bottled products described below, but canning is not described due to the high costs of equipment and cans. Technical advice is also needed to find the correct processing rime and temperature time as it varies with different foods and different containers. This type of processing is not recommended for vegetables on a small scale due to the risk of food poisoning.

Details of the production of the above products are shown in the process flow diagrams (1-17).

PROCESS FLOW DIAGRAMS

3.1 Fruit Pulp

For use in drinks (including juice nectars, squashes, cordials, syrups, wine, spirits, vinegar) and preserves.

PROCESS

NOTES

Harvest

Mature fruit, harvested carefully. Except for hard fruits (e.g. coconuts) they should not be piled into vehicles. Use containers (Fig. 1) with loaded weight of 10 kg approx. Smaller and they will be thrown, larger and they will be dragged or dropped - both causing damage to food and container.

Sort/grade

Sort by size, colour, shape, maturity, skin defects (Table 2).

Clean

Wash in clean water. Use filters or chlorinate if necessary (one teaspoon of bleach per gallon of water), (Fig. 2).

Peel

By hand or by small scale equipment (Fig. 3). Wear gloves if manual peeling as acids (and in pineapple an enzyme) can damage skin. Use stainless steel knives and easily cleaned plastic or wooden cutting surfaces.

Pulp

Use a fruit press, fruit mill or pulper/sieve (Figs. 4-6). All metal in contact with fruit should be stainless steel. Some fruits are heated to increase juice yield and prevent browning. Citrus juices are extracted by a reamer or press (Fig. 7). Juice is strained manually through sieves and clear syrups/cordials produced using a fine cloth bag.

3.2 Fruit Juice

PROCESS

NOTES

Pulp

Procedures to produce pulp shown in Diagram 3.1.

Filter

Filter through a metal/plastic fine mesh sieve.

Heat

Heat quickly to 70° C in stainless steel pan or heating coil.

Fill/seal ¬ Bottle + cap

Bottles and caps sterilised by boiling in water for minimum of 10 min. Hot fill juice while bottles are hot to prevent breakage. Simple bottle capping machines are available (Fig. 15).

Pasteurise

Heat fill bottles in boiling water for 10-20 min., depending on the type of fruit used and the size of the bottle.

Cool

Cool in air or more rapidly in a bottle cooler (Fig. 8).

3.3 Squash

PROCESS

NOTES

Pulp

Procedures to produce pulp shown in Diagram 3.1.

Filter

Filter through a metal/plastic fine mesh sieve.

Mix ¬ sugar syrup

Heat a 50% solution of sugar to 90° C and mix in correct proportion with juice.

Heat

Heat quickly to 70° C in stainless steel pan or heating coil.

Fill/seal ¬ Bottle + cap

Bottles and caps sterilised by boiling in water for minimum of 10 min. Hot fill juice while bottles are hot to prevent breakage. Simple bottle capping machines are available (Fig. 15).

Pasteurise

Heat filled bottles in boiling water for 10-20 min., depending on the type of fruit used and the size of the bottle.

Cool

Cool in air or more rapidly in a bottle cooler (Fig. 8).

3.4 Cordial

PROCESS

NOTES

Pulp

Procedures to produce pulp shown in Diagram 3.1.

Filter

Filter through a metal/plastic fine mesh sieve and then through a fine cloth filter.

Mix ¬ sugar syrup

Heat a 50% solution of sugar to 90° C and mix in correct proportion with juice.

Heat

Heat quickly to 70° C in stainless steel pan or heating coil.

Fill/seal ¬ Bottle + cap

Bottles and caps sterilised by boiling in water for minimum of 10 min. Hot fill juice while bottles are hot to prevent breakage. Simple bottle capping machines are available (Fig. 15).

Pasteurise

Heat filled bottles in boiling water for 10-20 min., depending on the type of fruit used and the size of the bottle.

Cool

Cool in air or more rapidly in a bottle cooler (Fig. 8).

3.5 Syrup

PROCESS

NOTES

Pulp

Procedures to produce pulp shown in Diagram 3.1.

Filter

Filter through a metal/plastic fine mesh sieve.

Heat

Concentrate the juice slowly by simmering in an open stainless steel pan, with regular stirring to prevent burning, until the solids content reaches 75-80% measured by refractometer (Fig. 9).

Fill/seal ¬ Bottle + cap

Bottles and caps sterilised by boiling in water for minimum of 10 min. Hot fill syrup while bottles are hot to prevent breakage. Simple bottle capping machines are available (Fig. 15).

Cool

Cool in air or more rapidly in a bottle cooler (Fig. 8).

3.6 Nectar

PROCESS

NOTES

Pulp

Procedures to produce pulp shown in Diagram 3.1.

Mix ¬ sugar syrup

Heat a 50% solution of sugar to 90° C and mix in correct proportion with pulp.

Heat

Heat quickly to 70° C in stainless steel pan or heating coil.

Fill/seal ¬ Bottle + cap

Bottles and caps sterilised by boiling in water for minimum of 10 min. Hot fill nectar while bottles are hot to prevent breakage. Simple bottle capping machines are available (Fig. 15).

Pasteurise

Heat filled bottles in boiling water for 10-20 min., depending on the type of fruit used and the size of the bottle.

Cool

Cool in air or more rapidly in a bottle cooler (Fig. 8).

3.7 Wine

PROCESS

NOTES

Pulp

Procedures to produce pulp shown in Diagram 3.1.

Mix ¬ sugar syrup

Mix a 20% solution of sugar in correct proportion with pulp.

Ferment ¬ yeast + nutrient

Add yeast (2% by weight of pulp/sugar) and yeast nutrient (approx. 1 g per litre). Fit airlock (Fig. 10) and maintain temperature at 30° C. Ferment for 3-7 days or until gas production ceases.

Filter

Remove yeast and fruit pulp through fine cloth, sterilised by boiling for at least 10 min.

Clear

Replace in fermenter and add clearing agent (e.g. gelatine). Some pulps (e.g. banana, citrus) may also need pectolytic and/or amylolytic enzymes to produce a crystal clear wine. Decant cleared wine from sediment.

Fill/seal ¬ Bottle + cork

Bottles sterilised by boiling in water for minimum of 10 min. Fill into cold bottles. Simple bottle capping machines are available (Fig. 15).

3.8 Spirit

NOTES

PROCESS

Pulp

Procedures to produce pulp shown in Diagram 3.1.

Mix ¬ sugar syrup

Mix a 20% solution of sugar in correct proportion with pulp.

Ferment ¬ yeast + nutrient

Add yeast (2% by weight of pulp/sugar) and yeast nutrient (approx. 1 g per litre). Fit airlock (Fig. 10) and maintain temperature at 30° C. Ferment for 3-7 days or until gas production ceases.

Filter

Remove yeast and fruit pulp through fine cloth, sterilised by boiling for at least 10 min.

Distill

Heat to 70-80° C depending on the altitude above sea level and collect the distillate fractions in a condenser.

Standardise

Adjust the alcohol (ethanol) content to 15-25% by volume for fortified wine, and for a spirit using a hydrometer 30-50%.

Fill/seal ¬ Bottle + cap

Bottles and caps sterilised by boiling in water for minimum of 10 min. Fill into cold bottles. Simple bottle capping machines are available (Fig. 15).

3.9 Vinegar

PROCESS

NOTES

Pulp

Procedures to produce pulp shown in Diagram 3.1.

Mix ¬ sugar syrup

Mix a 20% solution of sugar in correct proportion with pulp.

Ferment ¬ yeast + nutrient

Add yeast (2% by weight of pulp/sugar) and yeast nutrient (approx 1g per litre). Fit airlock (Fig. 10) and maintain temperature at 30° C. Ferment for 3-7 days or until gas production ceases.

Filter

Remove yeast and fruit pulp through fine cloth, sterilised by boiling for at least 10 min.

Clear

Replace in fermenter and add clearing agent (e.g. gelatine). Some pulps (e.g. banana, citrus) may also need pectolytic and/or amylolytic enzymes to produce a crystal clear wine. Decant cleared wine from sediment.

Ferment ¬ acetic acid

Add acetic acid bacteria (or less desirably bacteria allow natural contaminating bacteria to act) and ensure a plentiful supply of air to convert the alcohol in the wine to acetic acid.

Filter

Remove cloudiness using a fine cloth, sterilised by boiling for at least 10 min.

Standardise

Adjust the acetic acid content to 6-10% by blending with other batches and/or distilling part of the vinegar.

Fill/seal ¬ Bottle + cap

Bottles and caps sterilised by boiling in water for minimum of 10 min. Fill into cold bottles. Simple bottle capping machines are available (Fig. 15).

3.10 Fruit in Syrup

PROCESS

NOTES

Harvest

Mature, but not over-ripe fruit, harvested carefully and transported in containers (Fig. 1) with loaded weight of 10 kg approx. to prevent bruising.

Sort/grade

Sort by size, shape, maturity (Table 2).

Clean

Wash in clean water.

Peel

By hand or by small scale equipment (Fig. 3). Wear gloves if manual peeling as acids (and in pineapple an enzyme) can damage skin. Use stainless steel knives and easily cleaned plastic or wooden cutting surfaces.

Slice/destone

By hand or small machine to remove stone or seeds and cut into slices, halves etc.

Fill/Mix ¬ Hot sugar syrup
Fill/Mix ¬ Jars

Place fruit in container and add 50% sugar syrup heated to 90° C. Jars and lids sterilised by boiling in water for minimum of 10 mins. Hot fill while bottles are hot to prevent breakage.

Seal ¬ lids

Small lid sealers available (Fig. 11).

Pasteurise

Heat filled bottles in boiling water for 10-20 min., depending on the type of fruit used and the size of the bottle.

Cool

Cool in air or more rapidly in a bottle cooler (Fig. 8).

3.11 Preserves (jams, jellies)

PROCESS

NOTES

Pulp (and filter for jellies only)

Procedures to produce pulp shown in Diagram 3.1. Some jams also contain whole fruit pieces. For jellies the pulp is filtered through mesh and fine cloth until it is crystal clear.

Mix ¬ sugar
Mix ¬ acid
Mix ¬ pectin

Add sugar (approximately equal weight to fruit pulp depending on recipe) and mix in correct quantites of citric acid (to obtain pH 3.0-3.3) and, for some fruits, pectin (approximately 2% by weight). Precise formulation found by experimentation.

Heat

Heat quickly in stainless steel pan, with constant stirring to prevent burning, until soluble solids content reaches 68-72% as measured by refractometer (Fig. 9).

Fill/seal ¬ jars + lids

Bottles and caps sterilised by boiling in water for minimum of 10 min. Hot fill while bottles are hot to prevent breakage. Small lid sealers available (Fig. 11).

Cool

Cool in air or more rapidly in a bottle cooler (Fig. 8).

3.12 Preserves (marmalade)

PROCESS

NOTES

Pulp

Procedures to produce pulp shown in Diagram 3.1. Small scale equipment is shown in Fig. (7) for citrus fruits.

Filter

Through a metal/plastic fine mesh sieve and then through a fine cloth filter to produce a crystal clear juice.

Mix ¬ sugar
Mix ¬ acid
Mix ¬ pectin
Mix ¬ peels

Add sugar (weight depends on recipe) and if necessary mix in correct quantites of citric acid (to obtain pH 3.0-3.3) and, for some fruits, pectin (approximately 2% by weight). Precise formulation found by experimentation. Thinly sliced citrus peels are boiled in 60% sugar syrup for 15 min. and stored in the syrup for a minimum of 24 hours. For longer storage, up to six months, a chemical preservative (e.g. 1.8% sodium benzoate can be used).

Heat

Heat quickly in stainless steel pan, with constant stirring to prevent burning, until soluble solids content reaches 68-72% as measured by refractometer (Fig. 9).

Fill/seal ¬ jars + lids

Jars and lids sterilised by boiling in water for minimum of 10 min. Stir to ensure even distribution of peels and hot fill while jars are hot to prevent breakage. Small lid sealers available (Fig. 11).

Cool

Cool in air or more rapidly in a bottle cooler (Fig. 8).

3.13 Vegetable Products

PROCESS

NOTES

Harvest

Mature vegetable, harvested carefully. Except for hard vegetables (e.g. root crops) they should not be piled into vehicles. Use containers (Fig.1) with loaded weight of 10 kg approx. Smaller and they will be thrown, larger and they will be dragged or dropped - both causing damage to food and container.

Sort/grade

Sort by size, colour, shape, maturity, skin defects (Table 2).

Clean

Wash in clean water. Use filters or chlorinate if necessary (one teaspoon of bleach per gallon of water) (Fig. 2).

Peel/trim

By hand or by small scale equipment (Fig. 3) to remove skins, outside leaves etc. Use stainless steel knives and easily cleaned plastic or wooden cutting surfaces.

Slice

Manually or using small cutters.

3.14 Dry Salted Vegetables

PROCESS

NOTES

Sliced vegetable

Prepare vegetables as shown in Diagram 3.13.

Mix ¬ salt

Place alternate 3-5 cm layers of salt and vegetable in a wooden or food grade plastic container.

Prepare

Wash excess salt from vegetable and use as fresh material.

3.15 Brined Vegetables

PROCESS

NOTES

Sliced vegetable

Prepare vegetables as shown in Diagram 3.13.

Mix ¬ salt
Mix ¬ water
Mix ¬ sugar
Mix ¬ vinegar
Mix ¬ spices

Prepare a brine containing some or all of the ingredients according to the type of product required (Table 1) and to taste (e.g. in the choice of spices, amount of sugar etc.). Heat to 80-90° C.

Fill/seal ¬ jars + lids

Jars and lids sterilised by boiling in water for minimum of 10 min. Hot fill brine onto vegetables in jars while jars are hot to prevent breakage. Small lid sealers available (Fig. 11).

Pasteurise

Heat filled jars in boiling water for 10-20 min., depending on the type of vegetable used and the size of the jar.

Cool

Cool in air or more rapidly in a jar cooler (Fig. 8).

3.16 Pickles

PROCESS

NOTES

Sliced vegetables or fruits (or whole prepared vegetables)

Prepare vegetables as shown in Diagram 3.13. and fruits as shown in Diagram 3.1.

Mix ¬ salt
Mix ¬ water
Mix ¬ (sugar)

Prepare a brine containing ingredients according to the type of product required (Table 1) and to taste (e.g. the use of sugar or different fruit and vegetable mixtures). Store vegetables for up to 18 months in food grade plastic or wooden barrels to allow natural fermentation to precede. Ensure that vegetables are held below surface of brine at all times (Fig. 12).

Fill/seal ¬ jars + lids

Remove from barrels and repack in jars. Jars and lids sterilised by boiling in water for minimum of 10 min. Fill new brine/vinegar onto vegetables in jars. Small lid sealers available (Fig. 11). Final salt content = 2-6%, final acetic acid content = 6-10%.

Fill/seal ¬ brine/vinegar


Pasteurise

Heat filled jars in boiling water for 10- 20 min., depending on the type of vegetable used and the size of the jar.

Cool

Cool in air or more rapidly in a jar cooler (Fig. 8).

3.17 Sauces

PROCESS

NOTES

Sliced vegetables/fruits

Prepare vegetables as shown in Diagram 3.13 and fruits as shown in Diagram 3.1.

Pulp

Prepare a pulp from raw/cooked vegetables manually or using small pulping machines (Figs. 4-6).

Mix ¬ salt
Mix ¬ water
Mix ¬ sugar

Prepare a brine containing some or all of the ingredients according to the formulation for the product required and to taste (e.g. in the choice of spices, amount of sugar etc.).

Heat ¬ vinegar
Heat ¬ spices

Heat to 80-90° C with constant stirring. Add vinegar at end of heating to give final concentration of 2-6% salt and 6-10% acetic acid.

Fill/seal ¬ bottles/jars + lids

Jars and lids sterilised by boiling in water for minimum of 10 min. Hot fill sauce into bottles or jars while jars are hot to prevent breakage. Small lid sealers available (Fig. 11). Simple bottle capping machines are available (Fig. 15).

Cool

Cool in air or more rapidly in a jar cooler (Fig. 8).

ADDITIONAL PROCESSING NOTES

Cutting to Pieces of Food and Pulping

Chopping, de-stoning, slicing, dicing and grating form large to medium sized pieces. The purpose is to make food more uniform and more attractive, to allow uniform heat penetration or drying rates, and even mixing. Pulping can be done by hand, by a fruit press, a fruit mill or hand pulper/siever. All metal in contact with the fruit should ideally be stainless steel. Some fruits are heated before pulping to give a higher juice yield and to stop browning.

Salt and Sugar

These have similar actions at high concentrations (16% salt and 65% sugar) in preventing microorganisms from growing. The high concentration preserves the food by both drawing out water from the food and in the case of salt, by its anti-microbial properties and interference with the action of enzymes.

Acid and Alcohol

The natural acids of fruits help in preservation of jams, juices etc., and vegetables may be acidified by adding vinegar or fermenting to produce lactic acid and make pickles. The amount of sugar added to acidic foods such as jams or pickles, is found by the following formula:

% sugar = 80 - (20 x % acid present)
when the acid is measured as acetic acid.

For example, if the food has 2% acetic acid, 40% sugar should be added to adequately preserve the food. Advice on the measurement of acid concentration should be sought when starting production, but once found, the result can be used routinely without further technical advice.

In the fermentation of wines and beers it is important to use yeasts that are specifically bred for alcohol production and not rely on natural contaminating yeasts which may produce acids and give variable product quality and high losses through spoilage. An example of natural fermentation is palm wine where the shelf life does not exceed 12 hours due to contaminating micro-organisms which produce acid.

Other important factors include the acidity of the fruit which may have to be adjusted to give good fermentation by the yeast, and yeast nutrient which helps the yeast to grow rapidly and therefore produce a rapid fermentation. After the fermentation the yeast settles out and is removed. This should produce a clear drink, with no flavour of the yeast, but additional clarification is often necessary with many fruit juices and pulps used in winemaking. Great attention must be paid to hygienic conditions to stop the growth of unwanted micro-organisms. Sterilising chemicals (e.g. sodium metablsulphite or Camden tablets) and/or boiling water are essential to sterilise all processing equipment. Sulphur dioxide can be tasted at concentrations above 500 ppm (mg/kg) and all traces should therefore be removed from equipment to avoid contamination of the products.

QUALITY CONTROL

Hygiene

Large quantities of water are often used in fruit and vegetable processing and water quality is a key factor in overall product quality. Well water is often contaminated and a variety of water filters are available to purify it. However, these are often slow and an alternative solution is to chlorinate water. This can be done by adding one teaspoonful of bleach per gallon of water. It is strongly recommended that expert advice is sought on the suitability of available water in a particular area.

Strict hygiene should be observed at all times during processing. Clean aprons or overalls should be worn. Gloves should be used when preparing fruit as the acid, and in some cases, enzymes (for example, in pineapple) can damage the skin. Good water quality and hygienic conditions are needed to prevent recontamination of the food. Surfaces should be made from metal, stone or plastic covered wood to allow proper cleaning, and all utensils should be thoroughly cleaned after use.

Stainless steel knives and plastic or wooden utensils should be used for fruit because they do not react with the acids in fruit (wooden utensils, including cutting boards, are more easily cleaned than wooden tables. Wooden utensils can therefore be used, but not wooden tables). Copper, iron and brass should not be used because they produce off-flavours in the food.

In the production room floors should be sloping concrete for proper cleaning and drainage. Walls should be smooth for cleaning and there should be no ledges or rafters which could collect dust, bird droppings etc. Windows and doors should be netted to reduce insect contamination of the product During processing, the workers should wash their hands, wear clean overalls and not smoke. All work surfaces should be cleaned after each days production. If a worker is ill, especially with a stomach complaint, he/she should not be allowed to work that day. Local public health regulations should be understood and followed. This is especially important in vegetable processing where the low acidity of the product increases the risk of transmitting food poisoning bacteria to the food.

Quality control is used to make sure that the quality of food is the same for every batch each day. This is important because when customers buy food they expect it to be the same as the last time. If it is not, they will loose confidence in the product and stop buying it. Quality control is also useful to control production costs and identify parts of the process that are too expensive. Quality control is also needed to ensure that the food meets local legal limits (for example the % fruit in jam, the amount and type of preservatives, the weight of food in a jar or bottle and local labelling laws). Details of these laws should be found out before production starts.

Raw Material Control

All raw materials should be harvested when fully mature but (except for fruit that is to be pulped) not over-ripe. The appearance of the skin, fruit hardness, and colour can be examined during sorting/grading in a small scale enterprise. Taste can be assessed by the ripeness (colour, odour, size and hardness). Information about the internal condition of the fruit can be found by the presence of surface defects such as scabs and blight.

Raw materials should be clean, free of mould/yeast/bacterial contamination, insect damage and without serious bruising, splitting etc. Skin defects are less serious if the fruit or vegetable is to be peeled, but these may also indicate more serious internal damage. A summary of the factors to examine in the control of raw material quality are summarised in Table 2.

Table 2: Quality Control Factors for Raw Material Control

Product

Size

Shape

Colour

Maturity

Skin Blemish

Insect/Microbial Damage

All fruit drinks



·

·


·

Fruit in syrup

·

·

·

·


·

Preserves

some


·

·

some

·

Dry salt/pickles

some

some

·

·

some

·

Sauces


·

·


·


Process Control

Raw materials should be carefully washed to prevent soils, insects etc. from contaminating the final product, and sorted/peeled to remove unwanted parts of the plant. The main process control points for the products in this chapter are shown in Table 3.

Table 3: Process Control Points

Product

Weight of Ingredients

Heating Time & Temperature

Sugar Conc'n*

Acid Conc'n*

Salt Conc'n*

Alcohol Conc'n*

Juice

·

Squash

·

·

·

Cordial

·

·

·

Nectar

·

·

·

Syrup

·

Wine

·

·

·

Spirits

·

·

·

Vinegar

·

·

·

Fruit in syrup

·

·

·

Preserves

·

·

·

Dry salt vegetables

Brined vegetables

·

·

·

·

Pickles

·

·

·

·

·

Sauces

·

·

·

·

·

QUALITY CONTROL EQUIPMENT

Scales

Thermometer

Refract
-ometer

Ph meter**

Hydrometer

(Fig. 9)

* Conc'n = concentration

** Salt meters are available but unlikely to justify the relatively high cost. Technical advice on salt determination by titration should be sought.

Product Control

All products are assessed by one or more of the following criteria: texture/consistency, colour, flavour/taste, odour. Consumer studies should be undertaken to find the most acceptable product formulations. Raw material and process control should then be used to ensure that quality is reproduced in every batch.

PACKAGING AND STORAGE

Each of the products described is suitable for packing into glass containers. The main quality control procedures are to ensure that there is a correct fill weight (as displayed on the label) and to ensure that the containers are safe (free from glass splinters, cracks and soils) and that they are properly sealed. Most products, if they are properly processed, should have a shelf life in excess of 6 months and up to a year if stored in cool dark conditions.

Packaging

There is a general problem in packaging foods at a small scale. Packaging is expensive, may not be available on a regular basis and may form the largest single production cost. The main types that are used for fruit and vegetable products are: glass or plastic containers, or plastic bags.

Glass

The advantages of glass are that it is smooth, hygienic, easily cleaned, reusable (with new lids) and stackable. It also gives a better appearance to the product which increases customer acceptability and makes the food more valuable. The disadvantages are that it is breakable, expensive and heavy (therefore causing high transport costs). If the containers are reused care should be taken to make sure that they are thoroughly cleaned by washing in soapy water and rinsing in clean water. Bottle washers are available (Figs. 13-14). The containers should be sterilised with hot water, or steam. Do not place them directly into boiling water as they will break. They should be heated slowly to boiling and held at that temperature for at least 10 minutes. Bottles can be cooled in a continuous cooler (Fig. 8) when they contain juices, pickles or sauces. Jams must be stationary when they cool to allow the gel to form.

Plastic Bottles and Jars

These are available in some places and are cheaper than glass. However, they are not reuseable and form a poorer seal. This can lead to insect contamination, or in pickles to loss of acetic acid vapour, and hence a shorter shelf life. They should be washed with hot water, but the container is unable to withstand boiling temperatures. The product is therefore difficult to hot fill and may need preservatives to give the required shelf life.

Plastic Film

This is suitable for sachets or small packages of sauces, jams and chutneys. The plastic does not protect the food as well as the solid containers and the product therefore has a shorter shelf life.

Sealing

Simple hand sealers are available for jars and bottles (Figs. 11 & 15). Films can be sealed by an electric sealer or by a candle flame when the film is folded over a hacksaw blade.

Equipment

Fruit and Vegetable

· Water filter (Fig. 2)
· Peeling equipment (Fig. 3)
· Pulping equipment (Fig. 4-7)
· Sealing machines (Figs. 11-15)
· Bottle/jar cooler (Fig. 8)
· Refractometer (Fig. 9)
· Hydrometer
· Fermenter and air lock (Fig. 10)

Further Reading

Adams, M.R. (1980)

Small Scale Production of Vinegar from Bananas. TDRI Post Harvest Technology Publication, G132 56/62 Grays Inn Road, London, UK

Bielig, H.J. (1973)

Fruit Juice Processing FAO Agricultural Services Bulletin 13, FAO, Rome.

Finstead R., Devey,

Pickle and Sauce Making Food Trade Press Ltd. London, UK

J.D. & Dakin, J.C. (1971)


Fernandez, R., Cooke R.D., Quiros, R., Madrigal, L., Samuals, A. Aguilar, F., & Orfiz, A. (1980)

Fruit and Vegetable Processing and Appropriate Technology in Costa Rica; A Case Study. Tropical Science, 1980. 22 (2)

Mabey, D. & R. (1985)

Jams, Pickles and Chutneys Harmondsworth, UK (Penguin Publ)

Min. of Agriculture and Food (1969)

Home Preservation of Fruit and Vegetables Bulletin 21, Fisheries Her Majesty's Stationery Office, 49 High Holborn, London WC1

Rauch, G.H. (1965)

Jam Manufacture Leonard Hills Books, London

Turner, B.C. (1970)

Home Wine Making and Brewing Boots Company Ltd., London

US Department of Agriculture

Preservation of Vegetables by Salting or Brining. Farmers Bulletin, No. 1932.

FAO

Rural Home Economic Food Preparation, Series 1 Food Presearvation, Series 2 Labour Saving Ideas, Series 3 FAO, Via delle Terme di Caracalla, 00100 Rome, Italy.

Ihekoronye, A.I, and Ngoddy, P.O. (1985)

Integrated Food Science and Technology for the Tropics. Macmillan Publishers. London. UK

International Women's Tribune Centre (1984)

Women and Small Business International Women's Tribune Centre, 777 UN Piaza, New York, NY 10017, USA.

Jackelen, H.R. (1983)

Management for Commercial Analysis of Small Scale Projects. AT International, 1724 Massachusetts Avenue, N.W. Washington, DC20036, USA.

ILO-SDSR

Makala Ya Mafunzo. (Catalogue of Items of Appropriate Technology) Skill Development for Self Reliance. ILO/SDSE, PO Box 60598. Nairobi, Kenya.

VITA (1970)

Village Technology Handbook VITA College Campus, Schenectady, New York 12308, USA.


Figure 1 BOXES FOR HARVESTING


Figure 2 BLEACHING

USE CLEAN CHLORINATED WATER.
WASH YOUR HANDS.
WEAR A CLEAN APRON OR COAT.
WEAR GLOVES.
USE METAL, STONE OR PLASTIC TABLE SURFACES
INSTEAD OF WOOD.


Figure 3 PEELING MACHINE


Figure 4 FRUIT PRESS


Figure 5 FRUIT PRESS


Figure 6 FRUIT PRESS


Figure 7 PULP PRESS


Figure 8 BOTTLE COOLER


Figure 9 REFRACTOMETER


Figure 10 AIRLOCK


Figure 11 JAR SEALER


Figure 12 FERMENTATION OF VEGETABLES


Figure 13 BOTTLE WASHERS


Figure 14 BOTTLE WASHERS


Figure 15 BOTTLE SEALER

4.1 Malted Cereal Grain

PRODUCT/PROCESS DESCRIPTION

Germinated (sprouted or malted) grains are used in beer making. An enzyme (amylase) converts carbohydrates in the grain into simple sugars which are then convened to alcohol by yeast during beer fermentation (Chapter 11). The quality of the malted grain depends on the amylase activity which in turn depends on the germination rime and conditions, and the quality (age, maturity and condition) of the grains.

Principles of Preservation and Methods of Processing

The principle of preservation is removal of water by drying to about 8% moisture content At this moisture content amylase does not function during storage and microbial growth is inhibited. The enzyme begins to act when the malted grain is rehydrated during brewing. The processing method involves storing moistened grains under carefully controlled conditions to induce germination and then drying the germinated grains.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Grain


Store

Store in a waterproof, well ventilated room. Protect from insects, rodents and birds

Clean

Remove light dust etc. by winnowing, din and sand by sieving.

Soak ¬ water

Soak clean grain in potable water for approximately 48 hours at room temperature. More or less time may be needed depending on the ambient temperature and this can be checked by observing the time needed for maximum swelling of grains.

Germinate

Drain the water and place grain on a container that will allow air circulation (e.g. gauze/cloth/mesh). Cover with cloth or leaves to retain the moisture. Leave at room temperature until sprouts are 0.5-1.0 cm long.

Dry

Sun dry until fully dried.

Pack

Pack in gunny sacks, plastic sacks.

Store

Store in a cool dry store, protected against insects, rodents and birds.

QUALITY CONTROL

Hygiene

Drying inhibits the growth of almost all micro-organisms in the malted grain, but does not destroy them. Contamination by micro-organisms during processing results in them regrowing during beer fermentation to spoil the brew. High quality water used in processing and hygienic handling of moist grains are essential to prevent contamination of the product During storage the most important risk is from moulds which contaminate the product if proper storage conditions are not maintained.

Raw Material Control

The grains must be mature, dry and free from physical damage. Cleaning is done by winnowing to remove dust, light seeds and other foreign matter.

Process Control

Grain should be fully soaked until it swells and then properly drained in order that there is sufficient water to allow it to germinate. Too little time and germination is retarded, too much (or poor draining) and the grains may become contaminated with bacteria and rot. The grain should be allowed to fully germinate to obtain maximum amylase activity. Rapid sun drying is necessary to inhibit enzyme and microbial activity before the product spoils.

Product Control

The most important quality factor is the amylase activity, but it is rarely necessary to measure this at a small scale. The grains should be intact, free from mould and with an intact protruding structure (the radicle). In this condition the amylase activity is usually adequate for brewing.

PACKAGING AND STORAGE

The storeroom should be dry, cool and with adequate ventilation to prevent the growth of moulds. The absorption of moisture by the dry malted grains would also lead to a reduction in amylase activity.

The most important function is control of moisture content and suitable packaging materials include plastic sacks or containers if there is a risk from moisture uptake from the air. If the climate is sufficiently dry and there is little temperature variation in the store, sisal or jute sacks may also be used.

Equipment:

· No special equipment needed.

4.2 Cereal Flour (Maize and Sorghum)

PRODUCT/PROCESS DESCRIPTION

Cereal flours, especially from maize and sorghum are staple foods which have a high domestic demand. They are also used for the small scale production of bakery products, snackfoods and as ingredients in other foods. The flours are fine and white (although incorporation of different quantities of bran alter the colour to pale brown). Under correct storage conditions the flours have a shelf life of up to 2 years.

Principles of Preservation and Methods of Processing

The principle of preservation for flours is to reduce the moisture content to a level at which microbial and enzyme activity is inhibited. The process involves sorting, cleaning, conditioning and dehusking grains, grinding to a flour, and removing bran.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Dried Maize Seed


Clean

Son by hand to remove leaves, stones etc. - using winowing basket.

Condition

Add cold water to soften the maize.

Dehusk

Use dehusking machine (Fig. 1).

Soak

Soak grains for 3-4 days in water.

Dry

Sun dry for 3-5 hours.

Grind

Use grinding mill (Fig. 2).

Dry

Sun-dry the flour for 1-2 hours.

Sieve

Use a fine sieve, e.g. 1 mm aperture.

Pack

Use sealed plastic bags.

Store

Store in a cool dry place.

QUALITY CONTROL

Hygiene

As both the raw material and flour are in the dry state there is little risk of transmitting food poisoning bacteria. Good hygiene practices and careful storage are generally sufficient to maintain hygienic production.

Raw Material Control

Grains should be fully ripe, intact and free from mould, soils or other contaminants.

Process Control

The main quality control points are:

1) adequate conditioning of the grain to ensure that the correct amount of moisture has been absorbed to give good milling characteristics (i.e. the grains break down to a fine flour in the mill without shattering into pieces or clogging the mill),

2) the type of mill, speed and setting adjustment all affect the quality of the flour obtained,

3) sieve apertures determine the fineness of the flour,

4) adequate drying of flour to ensure that the expected shelf life is achieved.

Product Control

The main quality factors are colour and texture (fineness) of the flour. These are determined by the extent of conditioning, mill characteristics and extent of bran removal by sieving.

PACKAGING AND STORAGE

If the flour is produced in an area of low humidity, it may be stored in hessian or jute sacks. If it is produced in or transported to a region of higher humidity it may be necessary to package it in plastic sacks. In either case the store should be waterproof, cool and protected against birds, insects and rodents.

Equipment:

· Dehusker
· Grinding mill
· Scales (0-10 kg)
· Sieve

4.3 Popped Sorghum

PRODUCT/PROCESS DESCRIPTION

Popped sorghum is a crisp, white, expanded product about 0.5 cm in size made from sorghum grains and similar to popcorn. It has a sweet taste and the odour of sorghum. When processed and packaged correctly it has a shelf life of approximately 1 month. It is used as a snackfood and is sold in restaurants and bars.

Principles of Preservation and Methods of Processing

The principles of preservation are

1) destruction of enzymes and contaminating micro-organisms in the raw material by heat,

2) the removal of most of the moisture from the product to prevent recontamination during storage. The process also allows conversion of sorghum grain to a more acceptable product. It involves a rapid heating of moist sorghum grains to a high temperature. The rapidly increasing vapour pressure inside the grain causes it to burst or 'pop'.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Sorghum grains


Clean

Use a winnowing basket to remove light grains, leaves and dust. Remove stones, broken grains and unwanted materials by hand.

Soak

Soak in water to soften the bran for 3 min., and drain.

Pop

Pop the grain for 2 minutes in covered pans heated to 250° C.

Cool

Cool the popped grains on mats for 5 minutes, until they reach room temperature.

Separate

Hand pick to remove unpopped grains.

Pack

Package in airtight and moisture proof polythene bags.

Store

Store in a cool dry place.

QUALITY CONTROL

Hygiene

The high temperatures used in processing and the low moisture content of the product reduce the risk of spoilage and/or food poisoning by contaminating bacteria. Normal hygienic food handling practices should be used.

Raw Material Control

Grains should be ripe, fully mature, dry and free from mould growth. The moisture content of the grains should be 13-14%. Spoiled grains impart an unpleasant flavour and colour to the product, in addition to increasing the risk from aflatoxin poisoning.

Process Control

The control points are as follows:

1) The soaking time should be standardised at 3 minutes to optimise water uptake. Excessive water uptake results in delayed popping whereas a low water uptake results in charring of the product during popping.

2) The pan should be preheated to approximately 250°C before loading the grains as the best results are found with abrupt changes in grain temperature.

3) The product should be cooled rapidly after popping to prevent overcooking or excessive drying, and to prevent moisture vapour condensing inside the bag when the product is packaged.

PACKAGING AND STORAGE

Moisture uptake causes softening, mould growth and the development of rancidity. This is a dry, hygroscopic product and moisture absorption is minimised by packaging it in dry moisture proof containers such as heat sealed polythene bags. The storeroom should be clean, cool and dry.

Equipment:

· Heat sealer
· Scales (0-100g)

4.4 Sorghum Balls

PRODUCT/PROCESS DESCRIPTION

Sorghum balls are soft, sticky, light brown products made from popped sorghum pieces held together with sugar. The expected shelf life is approximately 2 weeks. It is used as a snackfood and is also sold in bars and restaurants.

Principles of Preservation and Methods of Processing

The principles of preservation are:

1) destruction of enzymes and contaminating micro-organisms in the raw material by heat,

2) the removal of most of the moisture from the product to prevent recontamination during storage. The process also allows conversion of sorghum grain to a more acceptable product.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Sugar


Heat

Heat slowly to avoid charring until it melts to a light brown liquid. Stir gently.

Mix ¬ popped sorghum

Add popped sorghum, stir continuously.

Heat

Heat gently for 2 minutes.

Mould

When cool enough to handle, mould into 4 cm diameter balls.

Cool

Place moulded balls on a tray to cool.

Pack

Pack in airtight, moistureproof polythene bags. Heat seal.

Store

Store in a cool, dry place.

QUALITY CONTROL

Hygiene

The high temperatures used in processing and the low moisture content of the product reduce the risk of spoilage and/or food poisoning by contaminating bacteria. Normal hygienic food handling practices should be used.

Raw Material Control

Popped sorghum grains should be sorted to remove broken or burned pieces and should be free from soils or other contamination.

Process Control

The control points are as follows:

1) Careful heating of the sugar with slow stirring is necessary to avoid charring and to produce the correct colour in the final product.

2) During mixing the graded sorghum is added slowly to the melted sugar with constant stirring to ensure even coating of the sugar to the sorghum. Overheating at this stage leads to darkening of the product.

3) Moulding the sugar coated product should produce uniform sized 4 cm diameter balls.

4) The product should be cooled rapidly after popping to prevent overcooking or excessive drying, and to prevent moisture vapour condensing inside the bag when the product is packaged.

PACKAGING AND STORAGE

Moisture uptake causes softening, mould growth and the development of rancidity. This is an hygroscopic product and moisture absorption is minimised by packaging it in dry moisture proof containers such as polythene or cellophane bags. The storeroom should be clean, cool and dry.

Equipment:

· Heat sealer
· Scales (0-100g)

4.5 White Rice

PRODUCT/PROCESS DESCRIPTION

White rice is widely consumed as a staple food. It is also used as an ingredient for other local food products (e.g. fried and roasted snackfoods such as rice doughnut, fermented foods such as rice beer and in weaning foods). The product is sold as either white (or polished) rice or brown (unpolished) rice. The shelf life is several months/years when properly stored.

Principles of Preservation and Methods of Processing

The principles of preservation are to heat the grain to destroy natural enzyme activity and then to remove moisture to prevent the growth of moulds during storage.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Paddy


Store

Store in waterproof, well ventilated room (Fig. 1). Keep sacks off the floor on pallets and protect against rodents. Store should be able to keep out animals, insects and birds.

Sort

Remove stones, insects etc. by hand, winnow, remove dust, stalk, leaves etc.



Pre-steam

Pre-steam the paddy at 100°C for approximately 30 mins.

Steep (soak)

Hot soak in water (60-80°C) for 4-6 hours.

Steam

Steam for an hour at 100°C.

Dry

Sun dry for 1-2 days in dry weather.

Dehusk/polish

Dehusking/polishing machines can be manually operated (Fig. 2) or diesel or electric powered.

Pack

Pack in paper/plastic sacks, or for the smaller quantities plastic or paper bags.

Store

Store in a waterproof, well ventilated room. Protected from insects and rodents. Shelf life up to 2 years depending on packaging and storage conditions.

QUALITY CONTROL

Hygiene

The heating stage during processing destroys most contaminating micro-organisms, but normal hygienic food handling practices should be used to prevent recontamination before the product is dried. It should be stored under conditions that prevent insect or rodent infestation.

Raw Material Control

Paddy should be harvested when fully mature and the harvest should be on time as a delay leads to over-drying and shattering of the grains. The grain must be properly stored in waterproof and well ventilated rooms to prevent absorption of moisture which would cause mould growth and discolouration. It should also be protected against rodent infestation, insects and birds. The grain should be sorted to remove stones, insects etc. and cleaned by winnowing to remove dust, stalk, leaves etc.

Process Control

The main control points are

1) parboiling and soaking of the grain at the correct temperature for the correct time reduces the steeping time and produces a desirable texture in the grain,

2) drying the grain for a sufficient time to prevent mould growth and make dehusking easier,

3) the holding time in the dehusking and polishing machines is optimised to reduce breakage of the grains and minimise the percentage of unhusked or unpolished grains in the final product.

PACKAGING AND STORAGE

The main control points are

1) the use of clean dry sacks or bags to avoid contamination and moistening of the grain,

2) control of fill-weights of packages using scales,

3) correct storage conditions to prevent moisture uptake by the grain and contamination by insects and rodents.

If the normal climatic conditions allow the grain to remain dry in the store it may be packaged in jute or sisal sacks. If it is transported to a more humid district it may be necessary to package in polythene sacks. Retail bags include paper packets for short term storage or heat sealed polythene bags for longer storage.

Equipment:

· Parboiler
· Dehusking mill
· Polishing mill
· Scales
· Bag sewing machine or heat sealer

4.6 Macaroni

PRODUCT DESCRIPTION

Macaroni is an extruded product made from wheat flour, which is formed into hard, crisp, dry, white/cream tubes approximately 4 mm in diameter and 2 cm long. It is used as pan of a main meal or as a snackfood.

Principles of Preservation and Methods of Processing

The principle of preservation is the removal of most of the moisture from the product to prevent recontamination during storage. The process also allows conversion of wheat flour into a more acceptable product.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Wheat flour


Sieve

Sieve to obtain fine flour using 0.5 mm sieve.

Mix

Mix 250 g flour with 5 g salt, spices and 50ml hot water to form stiff porridge/dough.

Extrude

Extrude using hand operated extruder with 4 mm diameter die.

Dry

Dry the long extuded noodles in the shade for 6 hours at 40-50° C.

Cut

Select for the correct size and color and cut into pieces up to 2 cm in length.

Pack

Pack in a dry moisture proof bag.

Store

Store in cool dry place.

QUALITY CONTROL

Hygiene

The low moisture content of the product reduces the risk of spoilage and/or food poisoning by contaminating bacteria. Normal hygienic food handling practices should be used.

Raw Material Control

Wheat grains should be sorted to remove broken or mouldy pieces and they should be free from soils or other contamination.

Process Control

The smoothness of the macaroni dough depends on the fineness of the flour and it is therefore sieved through a 0.5 mm sieve to remove larger particles. Hot water is added slowly and stirred gently to make a smooth stiff dough. Drying takes place in the shade to avoid rapid removal of water which would cause cracking/splitting of the macaroni. When fully dried the macaroni break when bent.

PACKAGING AND STORAGE

Moisture uptake causes softening, mould growth and the development of rancidity. This is a dry, hygroscopic product and moisture absorption is minimised by packaging it in dry moisture proof containers such as polythene or cellophane bags. The storeroom should be clean, cool and dry.

Equipment:

· Extruder
· Heat sealer
· Sieve
· Scales (0-100g)

4.7 Rice Noodles

PRODUCT/PROCESS DESCRIPTION

Rice noodles are hard, crisp, dry white tubes approximately 3 cm in diameter and 15 cm long, made from rice flour. They are used as part of a main meal or as a snackfood.

Principles of Preservation and Methods of Processing

The principle of preservation is the removal of most of the moisture from the product to prevent recontamination during storage. The process also allows conversion of rice flour to a more acceptable product.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Polished Rice

From Section 4.5.

Mill

Mill to a fine flour using manual or powered grinding machine.

Sieve

Sieve to obtain fine flour.

Mix

Mix the flour with hot water to form a stiff porridge/dough.

Extrude

Extrude using hand operated extruder with 2-3 mm diameter die.

Dry

Dry the long extruded noodles in shade for 6 hours.

Cut

Select for size and color and cut into pieces up to 15 cm in length.

Packaging

Pack in a dry moisture proof bag.

Store

Store in cool dry place.

QUALITY CONTROL

Hygiene

The low moisture content of the product reduces the risk of spoilage and/or food poisoning by contaminating bacteria. Normal hygienic food handling practices should be used.

Raw Material Control

Rice grains should be sorted to remove broken or mouldy pieces and should be free from soils or other contamination.

Process Control

The smoothness of the noodle dough depends on the fineness of the flour and it is therefore sieved through a 0.5 mm sieve to remove larger particles. Hot water is added slowly and stirred gently to make a smooth stiff dough. Drying takes place in the shade to avoid rapid removal of water which would cause cracking/splitting of the noodles. When fully dried the noodles break when bent.

PACKAGING AND STORAGE

Moisture uptake causes softening, mould growth and the development of rancidity. This is a dry, hygroscopic product and moisture absorption is minimised by packaging it in dry moisture proof containers such as polythene or cellophane bags. The storeroom should be clean, cool and dry.

Equipment:

· Mill
· Extruder
· Heat sealer
· Scales (0-100g)

4.8 Bread

PRODUCT/PROCESS DESCRIPTION

Bread and buns are leavened baked products based on wheat flour. They have a golden brown crust which may be soft or crisp, and a white honeycombed crumb. They are used as part of a main meal, packed meals, and as a snack. Breadcrumbs are also used as an ingredient and a binding agent by other food industries and domestically.

Principles of Preservation and Methods of Processing

The principles of preservation for bread and buns are:

1) to destroy enzymes, added yeast and contaminating micro-organisms by heat during baking, and

2) to remove water from the crust to inhibit mould growth. The expected shelf life is 3-5 days. The method of processing involves mixing ingredients to form a uniform dough, fermenting sugars in the dough to produce gas which leavens it, and baking to set the structure and texture of the dough and to develop the characteristic flavours, aromas and colour of the products.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Flour

Mixing ¬ salt
Mixing ¬ sugar
Mixing ¬ yeast
Mixing ¬ fat

Mix dry ingredients into smooth dough, then add yeast and water. Ratio: flour 62%, other ingredients (sugar, salt, yeast, fat) 5-10% and water 28-33%.

Mixing ¬ water

More or less water may be needed depending on the type of flour


or


2:1 flour to water, 1 tablespoon yeast/kg flour, 1 tablespoon sugar/kg flour, 1 tablespoon salt/kg flour.

Knead

Knead to a smooth elastic dough within 8-10 minutes by hand. More time may be required depending on the amount of dough but not exceeding 15 minutes. This stretches the gluten to allow full elasticity to develop in dough.

Ferment

Cover the dough with a piece of clean damp cloth and place it in warm place (30-40° C) for 35 minutes to allow yeast to act on sugars in the dough.

Divide and "knock back"

Divide dough into pieces according to capacity of tins available (e.g. 1kg flour will give 3 loaves of bread of 500 g each or 20 buns in a tin of 30x30 cm) and press gas out from dough. Form into correct shape. Round, roll and reshape according to the type of tins used. Cover with a damp clean cloth and leave to proof.

Proof

Proof in a warm place (30-40° C) without moving air for 45 min. to one hour.

Bake

Pre-heat oven to 200-250° C. Bake for 15-25 mins. depending on size of dough pieces.

Cool

Cool for at least one hour on cooling racks.

Pack

Pack in polythene bags, soft paper wraps.

Stoved

Store at room temperature on shelves, away from sunlight. Shelf life 3-5 days depending on storage conditions.

QUALITY CONTROL

Hygiene

Heat during baking kills almost all micro-organisms in the dough. The most important risk is from moulds which recontaminate the baked product if proper storage conditions are not maintained. However it is necessary to use good hygiene practices and potable water when preparing and handling dough to avoid excessive contamination and/or food poisoning bacteria which might survive baking.

Raw Material Control

Finely ground brown or white flour is used and should be free of insects and other contaminations. The yeast should be active (ie. alive) and it is therefore important to check the manufacturing/expiry date as old yeast will not raise the bread properly. Dried yeast should be activated by mixing with water and a little sugar and storing in a warm (30° C) place for 2-4 hours. Fresh (or compressed) yeast can be mixed with wate to form a paste and used directly. All ingredients should be weighed accurately as even a small variation can cause large differences in the final product.

Process Control

The main quality control points are

1) mixing/kneading to obtain a uniform dough,

2) the amount that the dough is raised during proofing - if left to raise too much the bread will collapse when put in the oven, if too little the bread will be small, dense and hard without the correct honeycomb texture,

3) the baking temperature and time control the development of flavour, colour and crust formation, and the correct texture in the crumb and crust. Control over the oven temperature and baking time is therefore essential.

Product Control

The main quality factors are colour, texture and aroma of the product. Each depends on the correct weighing and mixing of ingredients, and accurate control over baking time and temperature.

PACKAGING AND STORAGE

The main problem with these products during storage is mould growth and they should be stored in a dry, well ventilated and cool place. When left in the open air bread dries out to form a hard, unacceptable product. Depending on the expected shelf life, packaging can be a simple paper wrapper to prevent contamination by dirt, insects etc., or a plastic bag (polythene or cellophane). Bread and buns should not be packaged hot into plastic bags as moisture vapour will condense on the inside of the bag, wet the bread and cause mould growth. The weight of each loaf is determined by the weight of dough pieces and should be uniform from batch to batch.

Packaging

Suitable packaging materials are soft paper wrapping, cellophane or polythene bags which are often made specially for bread. Bags are usually tied in a knot instead of heat sealing.

Equipment:

· Electric mixer (optional)
· Rolling pins
· Oven
· Baking tins
· Clock
· Thermometer
· Scales (0-10 kg and 0-100g)
· Proofing room/oven
· Cooling racks

4.9 Biscuits

PRODUCT/PROCESS DESCRIPTION

Biscuits are produced from wheat flour in a large variety of shapes, sizes, textures and flavours. They generally have a golden brown crust with a crisp, pale brown crumb. For rapid baking the thickness of the biscuits is usually not more than 3-4 mm. They may be coloured with food dyes and dried fruit or nuts may also be incorporated. The shelf life is several months under correct storage conditions. They are eaten as snacks.

Principles of Preservation and Method of Processing

There are two principles of preservation: heat destruction of enzymes and micro-organisms during baking and removal of water during baking which inhibits spoilage micro-organisms during storage. The method of processing involves mixing ingredients to form a dough, rolling and forming into the desired shape and baking.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Flour

Cake flour.

Sieve

Use fine sieve - 1 mm aperture.

Mix

Mix 250 g flour + 65 g margarine + 100 g baking powder + pinch of salt. Mix by hand or with an electric mixer.

Mix

Mix in 1 egg + 20 g sugar + 15 g milk. Water can be used instead of milk.

Knead

Use small mixing machine to form a dough, or by hand.

Roll

Use a rolling stick/pin and board.

Cut

Cut to required size, e.g. round or square shape - use a hand cutter.

Bake

Bake at 200-250° C for 5-20 minutes.

Cool

Pack on a wire rack to reach room temperature.

Pack

Pack in sealed plastic packets.

Store

Store in a dry and cool place.

QUALITY CONTROL

Hygiene

Heat during baking destroys most contaminating bacteria and the dry product restricts recontamination during storage. Good hygienic practices should be enforced during preparation of the dough to prevent gross contamination and possible survival of large numbers of bacteria after baking.

Raw Material Control

The main quality factors are the colour and fineness of the flour and freedom from soils, mould, insects, weevils etc.

Process Control

The main control points are

1) accurate weighing and thorough mixing of ingredients, as even a small variation can cause large differences in the final product, and

2) time and temperature of baking, which controls the colour, texture, flavour and moistness of the product. If the temperature is too high the product will bum at the crust before the crumb is cooked. If it is too low the crumb will dry out before the crust colour is formed.

Product Control

The main quality factors are colour, size/shape, aroma, texture and flavour of the product, and freedom from blemishes, contamination and soils. Each is determined by the amounts and types of ingredients, control over mixing and baking stages and correct storage.

PACKAGING AND STORAGE

The product should be properly cooled before packaging into a moisture proof wrapper in order to prevent water vapour condensing onto the inside of the pack, moistening the biscuits and promoting mould growth. The pack also prevents contamination by soils, insects etc. The product should be stored in a cool, dry place away from sunlight which would accelerate rancidity.

Some biscuits, especially those that contain a high proportion of fat or those with cream fillings, require a more complex type of packaging than simple polythene. This may be a major limitation for a small scale processor and it is strongly advised that the availability and cost of packaging is investigated first if it is proposed to produce these type of biscuits. In all cases the package should be moisture proof, greaseproof and preferably lightproof.

Equipment:

· Mixer (optional)
· Cutter
· Rolling pin
· Oven
· Heat sealer
· Scales
· Thermometer
· Clock

4.10 Cakes

PRODUCT/PROCESS DESCRIPTION

Cakes made from wheat flour have a soft, golden brown crust with a soft, creamy white honeycomb crumb. They may be coloured with food dyes and dried fruit or nuts may also be incorporated. The shelf life is several days under correct storage conditions. They are eaten as a snack or as a dessert.

Principles of Preservation and Method of Processing

There are two principles of preservation: heat destruction of enzymes and micro-organisms during baking and removal of water during baking which inhibits spoilage micro-organisms during storage. A lesser preservative effect may result from high levels of sugar incorporated into the mixture.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Hour

Use Cake flour.

Sieve

Use fine sieve - 1 mm aperture.

Mixture

Mix baking powder + salt + 125 g margarine + 200 g sugar.

Mix

Add beaten egg, beat mixture until it becomes light, better using wooden spoon. Rub little oil and flour on a pan to prevent sticking of the batter.

Bake

Bake at 200-250° C for 15-20 minutes.

Cool

Cool on a cooling rack to room temperature.

Pack

Seal in plastic bags.

Store

Store in a dry cool place.

QUALITY CONTROL

Hygiene

Heat during baking destroys most contaminating bacteria and the relatively dry crust restricts recontamination during storage. Good hygienic practices should be enforced during preparation of the dough to prevent gross contamination and possible survival of large numbers of bacteria after baking.

Raw Material Control

The main quality factors are the colour and fineness of the flour and freedom from soils, mould, insects, weevils etc.

Process Control

The main control points are:

1) accurate weighing and thorough mixing of ingredients, as even a small variation can cause large differences in the final product, and

2) time and temperature of baking, which controls the colour, texture, flavour and moistness of the product. If the temperature is too high the product will bum at the crust before the crumb is cooked. If it is too low the crumb will dry out before the crust colour is formed.

Product Control

The main quality factors are colour, size/shape, aroma, texture and flavour of the product, and freedom from blemishes, contamination and soils. Each is determined by the amounts and types of ingredients, control over mixing and baking stages and correct storage.

PACKAGING AND STORAGE

The product should be properly cooled before packaging into a moisture proof bag in order to prevent water vapour condensing onto the inside of the pack, moistening the surface of the cake and promoting mould growth. The pack also prevents contamination by soils, insects etc. The product should be stored in a cool, dry place away from sunlight which would accelerate rancidity.

Equipment:

· Mixer (optional)
· Oven
· Heat sealer
· Scales
· Thermometer
· Clock

4.11 Chapati

PRODUCT/PROCESS DESCRIPTION

The pancake (chapati) is a round flat, unleavened bread product made from wheat dough. It has a soft brown/white mottled crust and a white honeycombed crumb. It is used as part of a main meal or as a snack and it is similar to the chapati and roti (India), the kisra (Sudan) and the tortilla (Latin America). In East Africa the Indian name 'Chapati' is used. The main difference between chapati and bread is the use of yeast in bread.

Principles of Preservation and Methods of Processing

The principles of preservation for chapati are

1) to destroy enzymes and contaminating micro-organisms by heat during frying,

2) to remove water from the crust to inhibit moulds. The expected shelf life is 3-5 days. The method of processing involves mixing ingredients to form a uniform dough, and 'dry' frying in oil to set the structure of the dough and develop the characteristic flavours, aromas and colour of the product.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Flour


Mixing ¬ coconut milk

Mix dry ingredients into a smooth mixture (at 37-40° C). Proportion 2:1 flour to water. If eggs are used, less water will be required. Salt to taste, fat is optional.

Mixing ¬ egg


Mixing ¬ salt ¬ fat


Knead

Knead to produce a smooth and elastic dough within 8-10 minutes by hand.

Relax (resting)

Shape the dough into smooth balls, cover with a clean piece of damp cloth. Rest for 10 min.

Divide

Divide dough into portions (1 kg flour will produce a minimum of 10-12 chapatis). Form into balls and cover with clean damp cloth.

Roll ¬ flour

Roll each piece into a floured surface using a rolling pin. Grease the surface of the dough with a little oil, form the dough into a ball, then roll again to a round piece 15 cm diameter and 2-3 mm thick, (diameter may be varied depending on the size of frying pan).

Fry ¬ oil

Grease a frying pan with a little oil and fry until surface is brown.

Cool

Cool to room temperature.

Pack

Pack in plastic bags.

Store

Shelf life is 2-5 days depending on storage conditions and packaging. Store in a cool dry place away from sunlight.

QUALITY CONTROL

Hygiene

Heat during frying kills almost all micro-organisms in the dough. The most important risk is from moulds which recontaminate the baked product if proper storage conditions are not maintained. However it is necessary to use good hygiene practices and potable water when preparing and handling dough to avoid excessive contamination and/or food poisoning bacteria which might survive baking.

Raw Material Control

Finely ground white flour is used and should be free of insects and other contamination. All ingredients should be weighed accurately as even a small variation can cause large differences in the final product.

Process Control

The main quality control points are

1) mixing/kneading to obtain a uniform dough,

2) the thickness of the rolled dough,

3) the frying temperature and time which control the development of flavour, colour and the correct texture in the crumb and crust. Control over the oil temperature and frying time is therefore essential.

Product Control

The main quality factors are colour, texture and aroma of the product. Each depends on the correct weighing and mixing of ingredients, rolling to uniform thickness and accurate control over frying time and temperature.

PACKAGING AND STORAGE

The main problem during storage is mould growth and chapatis should be stored in a dry, well ventilated and cool place. When left in the open air chapatis dry out to form a hard, unacceptable product. Packaging is used to prevent contamination by dirt, insects etc. Chapatis should not be packaged hot into plastic bags as moisture vapour will condense on the inside of the bag, wet the product and cause mould growth. The weight of each chapati is determined by the weight of dough pieces and this should be made uniform from batch to batch.

A suitable packaging material is a polythene bag which is usually tied in a knot instead of heat sealing.

Equipment:

· Electric mixer (optional)
· Rolling pins
· Scales (0-100g)
· Cooling racks

4.12 Unleavened Rice Bread

PRODUCT/PROCESS DESCRIPTION

Unleavened rice bread has a soft white spongy crumb and a brown crust. It is normally produced as 30 cm diameter cylindrical loaves which are cut to 4 cm slices for sale. The expected shelf life is 2 days and it is used to accompany a main meal and as a snackfood.

Principles of Preservation and Methods of Processing

The bread is preserved by heat destruction of enzymes and micro-organisms during baking. The product is more moist than wheat bread and the crust is less dried during baking, thus having less effect on preservation and a consequent shorter shelf life.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Polished Rice


Soak

Soak in clean water to soften the bran.

Drain

Drain excess water (for 10 min.) using a wire mesh.

Mill

Mill using a manual or powered mill.

Boil

Boil 1/3 of the flour in water to make a thin gruel.

Cool

Cool the gruel to body temperature.

Mix ¬ yeast

Mix the remaining flour (2/3) + yeast (5 g/kg + spices to taste and stir to form a smooth paste.

Mix ¬ spices


Mature

Keep the paste in a warm place (ie. just above room temperature (20-35° C) for 2 hours.

Mix ¬ sugar

Add sugar to taste, then mix slowly.

Bake

Pour paste in baking pans (30 cm diameter) and place in the oven at 250° C for 15-20 min.

Cool


Store

Store in a cool dry place.

QUALITY CONTROL

Hygiene

The high temperatures used in processing and the low moisture content of the product reduce the risk of spoilage and/or food poisoning by contaminating bacteria. Normal hygienic food handling practices should be used.

Raw Material Control

Rice grains should be sorted to remove broken or mouldy pieces and should be free from soils or other contamination.

Process Control

The main control points are

1) Control of heating during preparation of rice gruel to avoid overheating which causes excessive gelatinisation of the starch and results in uneven mixing with the unboiled portion of the flour.

2) The mixture should be cooled to body temperature (37°C) to avoid destruction of the yeast cells.

3) Thorough mixing is necessary to make a smooth homogeneous paste which in turn produces a uniform crumb in the final product.

4) During maturation keep the paste at a temperature between 20-35°C and avoid frothing to optimise the action of the yeast.

5) The time and temperature of baking are controlled to produce a golden brown crust. A knife plunged into the bread should not have adhering paste when the bread is fully baked.

6) The product should be cooled rapidly to prevent overcooking or excessive drying, and to prevent moisture vapour condensing inside the bag when the product is packaged.

7) The thickness of the slices is controlled to give uniform portions and expose the crumb for retail sale.

PACKAGING AND STORAGE

The product has a short shelf life and is generally not packaged. A paper cover may be used to prevent contamination by insects and dust. Moisture uptake causes softening, mould growth and the development of rancidity if the product exceeds the stated shelf life. The storeroom should be clean, cool and dry.

Equipment:

· Oven
· Mill
· Mixer (optional)


Figure 1 DEHUSKING MACHINE


Figure 2 GRINDING MACHINE

5.1 Packed Soyabeans

PRODUCT/PROCESS DESCRIPTION

Packed soyabeans are a dried product, sorted and packed into convenient quantities for domestic use. They are prepared into a relish for nsima or mixed with maize and groundnuts as a meal. The process outlined below is similar for other types of prepacked, dried grains and legumes.

Principles of Preservation and Methods of Processing

Preservation is achieved by removal of moisture which inhibits enzyme and microbial activity during storage. In more humid areas, moisture proof packaging may be necessary for a long shelf life (e.g. 6-12 months).

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Dried shelled beans

These are normally bought already shelled from the farmers.

Store

Store in sacks off the ground and take precaution against insect infestation and rodents.

Sort by hand

Sort to remove pebbles and leaves by hand.

Sieve

Sieve to produce uniform sized beans.

Winnow

Winnow to remove husks (small machines may be available).

Pack

Pack in plastic bags using scales + heat a sealing device.

Store

Store in a cool dry place.

QUALITY CONTROL

Hygiene

The raw material is dried in the field and as it is not moistened during processing, there is little risk of microbial contamination. Normal hygienic food handling is sufficient.

Raw Material Control

Beans should be free of husk, soils and other debris and free of insect damage. They should be stored in a cool dry room on raised pallets and protected from insects, birds and rodents.

Process Control

The quality of the product depends on its freedom from defects and uniformity (of size, and colour and fill weight). The main control points are therefore to effectively clean and sort the beans and to fill the declared quantity into each package.

PACKAGING AND STORAGE

The low moisture content of the product is maintained by packaging in sealed, strong moisture proof plastic bags and storing in a cool, dry place.

Equipment:

· Sieve
· Scales
· Heat sealer

5.2 Soy Milk

PRODUCT/PROCESS DESCRIPTION

Soy milk is a creamy white liquid extracted from soybeans and used as a dairy milk substitute. It can be sweetened with 5% sugar and consumed directly, or it can be flavoured with coffee, vanilla or fruit juices. It is also used to extend milk by mixing in a ratio of 1 pan dairy milk to 4 parts soy milk.

Principles of Preservation and Methods of Processing

Preservation is achieved by heat inactivation of enzymes, antinutritional factors such as trypsin inhibitors and micro-organisms. Recontamination is prevented by hermetically sealed packages. The process involves grinding soaked beans to a puree and then boiling with water and pressing to extract the milk.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Dried Soybeans


Cleaning

Remove any foreign material and wash with water.

Soak

Soak for 10 hrs in 10% sodium bicarbonate solution.

Grinding

Grind to a smooth paste or puree in a mortar and pestle, grain mill or blender.

Boil

The ground puree is boiled with water for 20 min. to extract the milk.

Press

Use a pressing sack or bag and squeeze or use a manual press. Two pressings are usual.

Boil

Bring milk to boil rapidly and boil for 6 minutes. Stir continuously.

Cool


Pack

Pack in bottles or plastic pouches.

QUALITY CONTROL

Hygiene

The extracted soy milk is a low acid product that is highly susceptible to spoilage and transfer of pathogenic bacteria to consumers. The methods used to handle the extracted milk therefore play an important role in determining the quality of the final product. Strict hygiene should be enforced when handling the extracted milk, and especially after boiling when the risk of recontamination is highest.

The main hygienic requirements are

1) thoroughly clean and sterilise (with chlorine solution or boiling water) all equipment and utensils used to handle the milk (e.g. filter bags, fillers) before and after processing (nb aluminium equipment should not be cleaned with chlorine solution),

2) strict enforcement of personal hygiene measures.

Raw Material Control

Beans should be free of husk, soils and other debris and free of insect damage. They should be stored in a cool dry room on raised pallets and protected from insects, birds and rodents.

Process Control

The main control points are

1) to soak the beans for an adequate time to allow proper grinding. If the beans are too hard through inadequate soaking the yield of milk will be reduced and the product will have a stronger beany flavour,

2) careful filtering of the milk through a fine mesh bag to reduce the solids content in the milk. Excess solids would settle out on storage and reduce the value of the product,

3) the time and temperature of boiling should be controlled to adequately pasteurise the milk and to destroy antinutritional factors in the milk. Continuous stirring should be used to prevent the product from burning onto the pan.

PACKAGING AND STORAGE

During packaging the most important quality control check is to ensure that filling equipment, bottles and caps are thoroughly cleaned and sterilised to prevent recontamination of the heat treated milk. This is especially important if the bottles are reused. Bottle fill weights should be accurately controlled.

Equipment:

· Grinding mill
· Press and pressing bags
· Bottle cleaner/steriliser
· Bottle filler
· Capping machine

5.3 Soy Flour/Composite Flour

PRODUCT/PROCESS DESCRIPTION

Soy flour is a fine creamy flour which is combined with maize flour or other cereal flours to increase the protein contained energy density and balance the amino acid composition of the composite flour. In this form it is used as a breakfast porridge and weaning food.

Principles of Preservation and Methods of Processing

Preservation is mostly achieved by the low moisture content of the flour which inhibits enzyme activity and microbial growth. A secondary benefit of mixing flours to form a composite flour is that the fat content of the mixed flour is lower than that of pure soya flour and the rate of deterioration due to rancidity is reduced.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Clean

Remove husks/pebbles and other debris using a winnower or winnowing baskets.

Boil

Boil in lime water (28 g calcium hydroxide/4.5 kg of beans is used. Water should be approx. 3x volume of solids.

Peel

Seed coats are peeled by rubbing in the palm of hands.

Dry

Sun dry on raised platforms.

Grind

Grind using a motar and pestle or a mill.

Sieve

Use fine (1 mm) sieve.

Mix

Mix 20:80 soybean flour: cereal flour. An electric mixer can be used.

Pack

Pack in polythene bags using a heat sealer and scales.

Store

Store in a cool dry place.

QUALITY CONTROL

Hygiene

The raw material and product remain dry throughout the process and hygiene problems are therefore less than for wet foods. However normal hygiene rules for safe rood handling should be observed.

Raw Material Control

Beans should be free of husk, soils and other debris and free of insect damage. They should be stored in a cool dry room on raised pallets and protected from insects, birds and rodents.

Process Control

Boiling is essential to remove the beany flavour/odour, to destroy a trypsin inhibitor in the beans which would reduce the nutritional value of the flour and to assist in removal of the seed coat. Drying to a low moisture content is a further control point to allow a production of a free-flowing flour during grinding, without clogging the mill. The sieve aperture determines the fineness of the flour and this should be similar to that of other cereal flours to allow thorough and uniform mixing. The proportions of each flour in the composite mixture should be weighed out carefully.

PACKAGING AND STORAGE

The flour is hygroscopic and should therefore be packaged into moisture proof containers (e.g. strong polythene bags) and fully sealed. Care is necessary to prevent the flour from contaminating the heat seal of a plastic bag and making it ineffective. The package should be filled carefully to the declared weight.

Equipment:

· Grinding mill
· Sieve
· Scales

5.4 Soy Coffee

PRODUCT/PROCESS DESCRIPTION

Soy coffee is a fine, brown powder made from roasted soybeans which is used as a coffee substitute by people who do not take coffeine for religious or health reasons.

Principles of Preservation and Methods of Processing

Preservation is achieved by heat inactivation of enzymes and micro-organisms and by removal of water to inhibit recontamination during storage. The process involves roasting soybeans and grinding to a powder.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Clean


Roast

Roast to a dark brown coffee colour in an oven.

Grind

Grind using a small electric grinding mill, or a motar and pestle.

Sieve

Sieve using a fine sieve (0.5 mm).

Blend

Mix with other batches to obtain uniform products.

Pack

Pack into glass jars or polythene bags.

QUALITY CONTROL

Hygiene

The heat treatment used in the process and the low moisture content of the product mean that this product is relatively free of the microbial dangers associated with wet low acid foods. Normal hygienic food handling is sufficient.

Raw Material Control

Beans should be free of husk, soils and other debris and free of insect damage. They should be stored in a cool dry room on raised pallets and protected from insects, birds and rodents.

Process Control

The main control points are the roasting and grinding stages of the process. Overheating leads to a burnt flavour and aroma and a colour that is too dark. Underheating produces lack of flavour and aroma, a colour that is too light and possibly incomplete inactivation of enzymes and contaminating micro-organisms. The particle size of the powdered product is determined by the extent of grinding and the aperture size of the sieve.

Product Control

The colour and aroma of the product can be made more uniform by blending different batches of powder.

PACKAGING AND STORAGE

The powder is hygroscopic and should therefore be packaged into moisture proof containers (e.g. strong polythene bags) and fully sealed. Care is necessary to prevent the powder from contaminating the heat seal of a plastic bag and making it ineffective. The package should be filled carefully to the declared weight.

Equipment:

· Oven
· Grinding mill
· Sieve
· Scales

6.1 Cassava Flour

PRODUCT/PROCESS DESCRIPTION

Cassava flour is a fine, white, powdery flour that has a shelf life of up to one year under correct storage conditions. It is widely used as a staple food and for the small scale production of a variety of fried and baked goods.

Principles of Preservation and Method of Processing

The low moisture content of the product inhibits enzyme activity and the growth of spoilage bacteria and moulds. The process involves softening the tubers, drying and then pounding/milling to produce the flour.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Fresh Cassava Tubers


Peel

Peel using vegetable knives.

Cut

Cut into 5-10 cm thick slices.

Soak

Pieces of tubers are soaked in water using 20-2001 buckets for 3-5 days to soften.

Separate

Fibres and other coarse materials are removed by hand.

Wash

Softened cassava is washed in clean water.

Dry

Sun dried for 2-3 days.

Mill/Pound

Mill using a maize mill or mortar and pestle.

Dry

Dry for 4-6 hours in the sun.

Sieve

1 mm sieve is used to sieve cassava to fine flour. Coarse material is re-pounded.

Pack

Pack in dry clean containers.

Store

Flour is stored in dry cool place.

QUALITY CONTROL

Hygiene

Fresh cassava is a moist, low acid food that is susceptible to bacterial and fungal growth. Hygienic practices, especially in the early stages of processing, should therefore ensure that contamination is minimised.

Raw Material Control

Fresh cassava should be free from microbial or insect damage and without serious bruising or cuts.

Process Control

The main control points are

1) the size of the cassava pieces, which controls the rate of softening and drying,

2) the temperature and relative humidity of the air (these factors are discussed in detail in Chapter 1, Dried Foods),

3) the extent of pounding/milling and the size of the sieve apertures which control the fineness of the flour.

Product Control

The main quality factors are colour and fineness of the flour and freedom from soils, insects etc. Colour and texture are determined by the rate of softening and drying, and type and extent of pounding/milling. Freedom from soils and insects is ensured by correct application of sorting and washing procedures and by ensuring that the product remains clean and protected from insects during drying and storage.

PACKAGING AND STORAGE

If the product is used in the area of production it is likely that it will remain dry without packaging materials, provided that the store is cool and dry without large temperature fluctuations. Jute or hessian sacks or baskets are usually sufficient. If it is to be transported to a more humid region, or if the weather becomes more humid, it may be necessary to package the product in moisture-proof sacks.

Equipment

· Sieve
· Grinding mill (optional)

6.2 Cassava Cakes

PRODUCT/PROCESS DESCRIPTION

Cassava cake has a golden brown crust with a soft, creamy white honeycomb crumb. It may be coloured with food dyes and dried fruit or nuts may also be incorporated. The shelf life is several days under correct storage conditions. It is eaten as a snack or as a dessert.

Principles of Preservation and Method of Processing

There are two principles of preservation: heat destruction of enzymes and micro-organisms during baking and removal of water during baking which inhibits spoilage micro-organisms during storage. A lesser preservatives effect may result from high levels of sugar incorporated into the mixture.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Cassava Flour

(see Section 6.1).

Mix

Mix flour with other ingredients as follows: 1 kg cassava flour, 125 g baking powder, 200 g sugar, 250 g stock margarine, 6 eggs and 1/2 litre milk or water to a smooth paste. Pour mixture in tins greased with margarine to avoid sticking.

Bake

Bake for 10-15 minutes until golden brown at temperatures of 180-200° C.

Cool

Cool to room temperature.

Pack

Pack in plastic bags to prevent cake absorbing moisture for the atmosphere or losing moisture to the atmosphere depending on the conditions.

Store

Store in cool place and not in sunlight to avoid rancidity.

QUALITY CONTROL

Hygiene

Heat during baking destroys most contaminating bacteria and the dry crust restricts recontamination during storage. Good hygienic practices should be enforced during preparation of the dough to prevent gross contamination and possible survival of large numbers of bacteria after baking.

Raw Material Control

The main quality factors are the colour and fineness of the flour and freedom from soils, mould, insects, weevils etc.

Process Control

The main control points are:

1) accurate weighing and thorough mixing of ingredients, as even a small variation can cause large differences in the final product, and

2) time and temperature of baking, which controls the colour, texture, flavour and moistness of the product. If the temperature is too high the product will bum at the crust before the crumb is cooked. If it is too low the crumb will dry out before the crust colour is formed.

Product Control

The main quality factors are colour, size/shape, aroma, texture and flavour of the product, and freedom from blemishes, contamination and soils. Each is determined by the amounts and types of ingredients, control over mixing and baking stages and correct storage.

PACKAGING AND STORAGE

The product should be properly cooled before packaging into a moisture proof bag in order to prevent water vapour condensing onto the inside of the pack, moistening the surface of the cake and promoting mould growth. The pack also prevents contamination by soils, insects etc. The product should be stored in a cool, dry place away from sunlight which would accelerate rancidity.

Equipment:

· Mixer (optional)
· Oven
· Heat sealer
· Scales
· Thermometer
· Clock

6.3 Cassava Scones

PRODUCT/PROCESS DESCRIPTION

Cassava scones are flat, cylindrical cakes approximately 10 cm in diameter and 1.5 cm thick. The texture is harder than cake and they are more salty and less sweet, but otherwise the products are similar. They have a shelf life of a few days under correct storage conditions and are used as a snackfood or in packed meals.

Principles of Preservation and Method of Processing

There are two principles of preservation: heat destruction of enzymes and micro-organisms during baking and removal of water during baking which inhibits spoilage micro-organisms during storage.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Cassava Flour

(See Section 6.1)

Mix

Mix flour with other ingredients as follows: 1 kg cassava flour, 75 g baking powder, 50 g sugar, 75 g stock margarine, 3 eggs, 1 teaspoon salt and 1/2 litre milk or water and mix to a smooth dough.

Roll

Place dough on a lightly floured table and roll it out to 1 cm thickness.

Cut

Cut the rolled dough into rounds using a tumbler. Left over pieces, are rolled again and cut into rounds.

Bake

Put the scones onto a greased baking tray. Do not allow the scones to touch each other to avoid them sticking together. Bake for 10-15 minutes till golden brown colour at a temperature of 180-200° C.

Cool

Cool to room temperature.

Pack

Pack in plastic bags.

Store

Store in cool place, avoid direct sunlight.

QUALITY CONTROL

Hygiene

Heat during baking destroys most contaminating bacteria and the dry crust restricts recontamination during storage. Good hygienic practices should be enforced during preparation of the dough to prevent gross contamination and possible survival of large numbers of bacteria after baking.

Raw Material Control

The main quality factors are the colour and fineness of the flour and freedom from soils, mould, insects, weevils etc.

Process Control

The main control points are

1) accurate weighing and thorough mixing of ingredients, as even a small variation can cause large differences in the final product, and

2) time and temperature of baking, which controls the colour, texture, flavour and moistness of the product. If the temperature is too high the product will bum at the crust before the crumb is cooked. If it is too low the crumb will dry out before the crust colour is formed.

Product Control

The main quality factors are colour, size/shape, aroma, texture and flavour of the product, and freedom from blemishes, contamination and soils. Each is determined by the amounts and types of ingredients, control over mixing and baking stages and correct storage.

PACKAGING AND STORAGE

The product should be properly cooled before packaging into a moisture proof bag in order to prevent water vapour condensing onto the inside of the pack, moistening the surface of the cake and promoting mould growth. The pack also prevents contamination by soils, insects etc. The product should be stored in a cool, dry place away from sunlight which would accelerate rancidity.

Equipment:

· Mixer (optional)
· Oven
· Heat sealer
· Scales
· Thermometer
· Clock

6.4 Cassava Fritters

PRODUCT/PROCESS DESCRIPTION

Cassava fritters are thin, round, fried products which are approximately 8 cm in diameter and 0.3 cm thick. They are made from fresh grated cassava bound together with egg and cassava flour. The texture is harder than baked products and they have a shelf life of a day or so. They are used as an appetiser, a snackfood or in packed meals.

Principles of Preservation and Method of Processing

The principle of preservation is heat destruction of enzymes and micro-organisms during frying. The short shelf life does not require inhibition of spoilage micro-organisms during storage.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Cassava


Grate

Grate cassava and onions using a fine grater.

Mix

Mix 4 cups grated cassava, 1/2 cup grated onions, 1/2 teaspoon salt, 3 eggs (beaten), 1 cup wheat/cassava flour and other spices. Consistency should be thick like a scone mixture.

Shape

Take spoonfulls of the moisture and shape into rounds 3 mm thick. Use floured hands to avoid sticking.

Coat/fry

Dip rounds into whisked egg and deep fry till both sides are golden brown.

Drain

Remove excess oil from fritters.

Cool

Cool to room temperature.

Pack

Seal into plastic bags.

Store

Store in a cool place, in the shade to reduce rancidity.

QUALITY CONTROL

Hygiene

Heat during frying destroys most contaminating bacteria and the short shelf life restricts recontamination during storage. Good hygienic practices should be enforced during preparation of the dough to prevent gross contamination and possible survival of large numbers of bacteria after frying.

Raw Material Control

The main quality factors are the colour and particle size of the grated cassava and freedom from soils, mould and insect damage. Oil used for frying should be clear, of good quality and free from rancidity (the quality characteristics of oil are described in more detail in Chapter 2 Cooking Oils).

Process Control

The main control points are

1) accurate weighing and thorough mixing of ingredients, as even a small variation can cause large differences in the final product,

2) the use of flour to prevent the batter sticking during forming,

3) coating with egg to prevent the product disintegating during frying,

4) time and temperature of frying, which controls the colour, texture, flavour and moistness of the product.

Product Control

The main quality factors are colour, size/shape, aroma, texture and flavour of the product, and freedom from contamination and soils. Each is determined by the amounts and types of ingredients, control over mixing and frying stages, In particular the type and quality of the frying oil is a major influence on the product quality.

PACKAGING AND STORAGE

The product is eaten within a few hours and packaging is rarely necessary except to keep the product clean. The product should be stored in a cool, dry place away from sunlight which would accelerate rancidity of the oil in the product.

Equipment:

· Mixer (optional)
· Scales
· Grater

6.5 Cassava Doughnuts

PRODUCT/PROCESS DESCRIPTION

Cassava doughnuts are thick, cylindrical, fried products which are approximately 8 cm in diameter and 3 cm thick. The texture is stiffer than cake and the crust is soft with a deep, uniform brown colour. They have a shelf life of a few days under correct storage conditions and are used as a snackfood or in packed meals.

Principles of Preservation and Method of Processing

There are two principles of preservation: heat destruction of enzymes and micro-organisms during frying and removal of water during frying which inhibits spoilage micro-organisms during storage. However the relatively high moisture content and high fat content result in a shorter shelf life than for cakes and scones.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Cassava Flour

See Section 6.1.

Mix

Mix 1kg cassava flour, 75 g baking powder, 200 g sugar, 6 eggs, 125 g margarine, 1/2 teaspoon salt and 1/2 litre milk or water. Mix to a smooth dough.

Shape

Shape with floured hands, take mixture in spoonfuls, shape into rounds with a hole in the middle.

Fry

Deep fry the doughnuts in hot oil (approx 150° C) until golden brown on both sides.

Drain

Remove excess oil.

Cool

Cool to room temperature.

Pack

Pack in plastic bags, preferably in units of 10 for easy counting and wholesale.

Store

Store in cool and shaded place to slow down rancidity.

QUALITY CONTROL

Hygiene

Heat during frying destroys most contaminating bacteria and the soft crust restricts recontamination during storage. Good hygienic practices should be enforced during preparation of the dough to prevent gross contamination and possible survival of large numbers of bacteria after frying.

Raw Material Control

The main quality factors are the colour and fineness of the flour and freedom from soils, mould, insects, weevils etc. Oil used for frying should be clear, of good quality and free from rancidity (the quality characteristics of oil are described in more detail in Chapter 2 Cooking Oils).

Process Control

The main control points are:

1) accurate weighing and thorough mixing of ingredients, as even a small variation can cause large differences in the final product,

2) time and temperature of frying, which controls the colour, texture, flavour and moistness of the product. If the temperature is too high the product will bum at the crust before the crumb is cooked. If it is too low the crumb will become filled with oil before the crust is fully formed.

Product Control

The main quality factors are colour, size/shape, aroma, texture and flavour of the product, and freedom from blemishes, contamination and soils. Each is determined by the amounts and types of ingredients, control over mixing and frying stages and correct storage. In particular the type and quality of the frying oil is a major influence on the product quality.

PACKAGING AND STORAGE

The product should be properly cooled before packaging into a moisture proof bag in order to prevent water vapour condensing onto the inside of the pack, moistening the surface of the cake and promoting mould growth. The pack should also be oil resistant and prevent contamination by soils, insects etc. The product should be stored in a cool, dry place away from sunlight which would accelerate rancidity of the oil in the product.

Equipment:

· Mixer (optional)
· Heat sealer
· Scales
· Thermometer

6.6 Makaka (Dried Cassava)

PRODUCT/PROCESS DESCRIPTION

Makaka is hard, dry, white pieces of cassava approximately 6-10 cm in size. They have a shelf life of 6-12 months under correct storage conditions and are widely used to produce flour, in brewing and for direct consumption after cutting to 2- 3 cm pieces and boiling.

Principles of Preservation and Method of Processing

The low moisture content of the product inhibits enzyme activity and the growth of spoilage bacteria and moulds. The process involves peeling the fresh cassava and sundrying.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Fresh Cassava Tubers


Peel

Use vegetable knives.

Cut

Cut into 10-20 cm pieces.

Wash

Wash using clean water.

Dry

Sun dry for 1-2 weeks.

Pack

Pack into sacks.

Store

Store in a cool dry place.

QUALITY CONTROL

Hygiene

Fresh cassava is a moist, low acid food that is susceptible to bacterial and fungal growth. Hygienic practices, especially in the early stages of processing, should therefore ensure that contamination is minimised.

Raw Material Control

Fresh cassava should be free from microbial or insect damage and without serious bruising or cuts.

Process Control

The main control points are the size of the cassava pieces, which controls the rate of drying, and the temperature and relative humidity of the air. These factors are discussed in detail in Chapter 1 (Dried Foods).

Product Control

The main quality factors are colour, texture and freedom from blemishes and soils. Colour and texture are determined by the rate of drying and freedom from blemishes and soils is ensured by correct application of sorting and washing procedures and by ensuring that the product remains clean during drying.

PACKAGING AND STORAGE

If the product is used in the area of production it is likely that it will remain dry without packaging materials, provided that the store is cool and dry without large temperature fluctuations. If it is to be transported to a more humid region, or if the weather becomes more humid, it may be necessary to package the product in moisture proof sacks.

Equipment:

· No special equipment required.

6.7 Potato Crisps

PRODUCT/PROCESS DESCRIPTION

Irish potato crisps are thin, round slices (1-2 mm thick) of potato which are fried to a light golden brown colour and crisp texture. They have a shelf life of several weeks if packaged and stored correctly. They are used as a snackfood or in packed meals.

Principles of Preservation and Method of Processing

The priciples of preservation are heat destruction of enzymes and micro-organisms during frying and removal of moisture to inhibit recontamination. Packaging is essential to prevent moisture pickup and retard rancidity of the oil in the product.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Irish Potatoes


Peel

Use vegetable knives.

Slice

Slice to 3-4 mm thick.

Wash

Wash slices with clean water.

Fry

Pry in 20 cm shallow frying pan to light brown colour.

Cool


Pack

Pack cooled crisps in plastic bags.

Store

Store in cool dry place.

QUALITY CONTROL

Hygiene

Heat during frying destroys most contaminating bacteria and the low moisture content restricts recontamination during storage. Good hygienic practices should be enforced during preparation of the potatoes.

Raw Material Control

The main quality factors are the colour and size of the potatoes and freedom from soils, mould and insect damage. Oil used for frying should be clear, of good quality and free from rancidity (the quality characteristics of oil are described in more detail in Chapter 2 Cooking Oils).

Process Control

The main control points are

1) thickness of the slices of potatoes which determines the rate of heat penetration,

2) time and temperature of frying, which controls the colour, texture, flavour and moistness of the product.

Product Control

The main quality factors are colour, size/shape, aroma, texture and flavour of the product, and freedom from contamination and soils. Each is determined by control over the frying stage. In particular the type and quality of the frying oil is a major influence on the product quality.

PACKAGING AND STORAGE

The product should be properly cooled before packaging into a moisture proof bag in order to prevent water vapour condensing onto the inside of the pack, moistening the product and promoting mould growth. The pack is also greaseproof and prevents contamination by soils, insects etc. The product should be stored in a cool, dry place away from sunlight which would accelerate rancidity of the oil in the product.

Equipment:

· Scales
· Heat sealer
· Slicing machine (optional)

6.8 Matobola (Dried Sweet Potatoes)

PRODUCT/PROCESS DESCRIPTION

Matobola is hard, dry, light brown pieces of sweet potatoes approximately 2-3 cm in size. They have a shelf life of 6-12 months under correct storage conditions and are used to produce flour, and for direct consumption.

Principles of Preservation and Method of Processing

Heat destroys enzymes and contaminating bacteria/moulds and the low moisture content of the product inhibits recontamination. The process involves peeling and boiling the fresh sweet potato and sundrying.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Fresh Sweet Potato


Wash

Wash to remove skins.

Boil

Washed potatoes are boiled for 30 min.

Cool

Cool to room temperature.

Peel

Remove peels by hand.

Slice

Potatoes are sliced in 3-5 cm thick slices.

Dry

Sliced pieces are sun dried for 1-2 weeks.

Pack

Dried potatoes are packed in sacks.

Store

Stored in cool dry place.

QUALITY CONTROL

Hygiene

Fresh sweet potato is a moist, low acid food that is susceptible to bacterial and fungal growth. Hygienic practices, especially in the early stages of processing, should therefore ensure that contamination is minimised.

Raw Material Control

Fresh sweet potato should be free from microbial or insect damage and without serious bruising or cuts.

Process Control

The main control points are the size of the pieces, which controls the rate of heat penetration and drying, the temperature and time of boiling and the temperature and relative humidity of the air. These factors are discussed in detail in Chapter 1 (Dried Foods).

Product Control

The main quality factors are colour, texture and freedom from blemishes and soils. Colour and texture are determined by the amount of heating and the rate of drying. Freedom from blemishes and soils is ensured by correct application of sorting and washing procedures and by ensuring that the product remains clean during drying.

PACKAGING AND STORAGE

If the product is used in the area of production it is likely that it will remain dry without packaging materials, provided that the store is cool and dry without large temperature fluctuations. If it is to be transported to a more humid region, or if the weather becomes more humid, it may be necessary to package the product in moisture proof sacks.

Equipment:

· No special equipment required.

7.1 Roasted Groundnuts

PRODUCT/PROCESS DESCRIPTION

Roasted groundnuts are whole or split nuts which are roasted to a light brown colour and a crisp texture. They are commonly salted and are used as a snackfood.

Principles of Preservation and Methods of Processing

Preservation is by the heat treatment during roasting and the low moisture content of the final product. Moisture proof packaging is necessary to achieve a shelf life in excess of a few days, but this product is often sold within a short time of preparation.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Nuts in shell


Shell

Shell using a manual or powered shelling machine.

Store

Store in gunny sacks, in a well-ventilated room; keep sacks on racks off the ground. Protect from rodents and storage pests.

Sort

Sort to remove mouldy, and shrivelled nuts.

Sieve

Sieve to obtain uniform sized nuts.

Clean

Clean by using a winowing basket to remove the dust

Roast

Roast the nuts on trays using dry heat to give a characteristic flavour, light brown and crisp texture.

Dehusk

Remove the skin by rubbing the nuts in a tray or a winowing basket when cooled.

Winnow

Use a winowing basket.

Salt

Sprinkle on salt to improve the taste.

Pack

Weigh the correct amount, pack in plastic bags and carefully heat seal the packets.

Store

Store in a cool dry place.

QUALITY CONTROL

Hygiene

The raw material and product remain dry throughout the process and hygiene problems are therefore less than for wet foods. However normal hygiene rules for safe food handling should be observed (Annex 1).

Raw Material Control

Groundnuts should be harvested when fully mature. If the nuts are left in the ground for too long after reaching maturity they lose flavour and colour. Early lifting before maturity produces shrivelled nuts that are difficult to process. The nuts should be dried in the field while in the shell, and then while still on the stalk, turned upside down. Drying groundnuts on iron sheets or a roof is not recommended because the nuts become baked and lose their flavour.

Process Control

It is very important to shell the nuts before storing and to dry them thoroughly to prevent mould growth beneath the shell. Some moulds produce 'aflatoxin', a poison which is highly dangerous. Shells, stones and leaves, shrivelled or mouldy nuts should all be removed. The quality of the final product is mostly determined by the time and temperature of heating (roasting) and the size and moisture content of the nuts. Other control points are the effectiveness of removing the brown paper husk by rubbing and winnowing, and the weight of salt added to the final product.

Product Control

The quality factors for roasted nuts are colour, taste/flavour, texture and uniform size. The colour flavour and texture are determined by the time and temperature of roasting and the size by grading the raw nuts.

PACKAGING AND STORAGE

The crispness and flavour of the product is maintained by packaging in sealed, mositure proof plastic bags and storing in a cool, dry place.

Equipment:

· Shelling machine
· Grinding mill
· Scales
· Heat sealer
· Sieve
· Roasting trays/pans

7.2 Groundnut Flour

PRODUCT/PROCESS DESCRIPTION

Groundnut flour is a fine whitely flour obtained from crushed, raw, dry groundnuts. It is a valuable product that has a large demand as a convenient food for domestic use, as an ingredient, in seasonings and garnishings, snackfoods, porridges and other foods.

Principles of Preservation and Methods of Processing

Groundnuts are already preserved in a dry form and have a long shelf life provided that they are well-dried and properly stored. In flour production the raw dry groundnuts are cleaned, crushed and sieved. When processing is carried out correctly the flour remains dry and microbial and enzyme action is therefore inhibited.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Groundnuts


Shell

Use a manual or powered shelling machine.

Store

Store in gunny sacks; in a well-ventilated room. Keep sacks on pallets off the ground. Protect from rodents and insects.

Sort

Remove mouldy, shrivelled nuts, stones etc. by hand.

Clean

Remove the dust using a winowing basket Remove some, but not all of the brown coat.

Crush/sieve

Crush with a small milling machine (Fig. 1). Sieve the crushed nuts through 0.5 mm mesh. Repeat to crush the smaller parts in a mortar with pestle, then sieve again.

Pack

Package in moisture proof plastic packets. Heat seal the packets.

Store

Store in a cool dry place.

QUALITY CONTROL

Hygiene

The raw material and product should remain dry throughout the process and hygiene problems are therefore less than for wet foods. However normal hygiene rules for safe food handling should be observed.

Raw Material Control

Groundnuts should be harvested when fully mature. If the nuts are left in the ground for too long after reaching maturity they lose flavour and colour. Early lilting before maturity produces shrivelled nuts that are difficult to process. The nuts should be dried in the field while in the shell, and then while still on the stalk, turned upside down. Drying groundnuts on iron sheets or a roof is not recommended because the nuts become baked and lose their flavour.

Process Control

It is very important to dry the nuts thoroughly to prevent mould growth beneath the shell, and to shell them before storing. Some moulds produce 'aflatoxin', a poison which is highly dangerous. Care should be taken if shelling is done by hand not to moisten the nuts. Grits, shells, stones and leaves, shrivelled or mouldy nuts should all be removed. The nuts should be completely dried before grinding to produce a high yield of flour. If the nuts are damp they will stick together and produce a cake instead of a free-flowing flour. The degree of grinding and the size of the sieve apertures determines the fineness of the flour. The flour should be weighed carefully, filled into packets and well sealed. Care is needed to prevent flour from becoming trapped in a heat seal, which would make it ineffective.

Product Control

The main quality factors are colour, texture and flavour of the product. The colour depends on the amount of brown seed coat ground together with the nuts. A small amount is necessary to improve the colour and to produce the desired texture. The flavour depends on the correct drying procedures being used.

PACKAGING AND STORAGE

The groundnut flour should be stored in an airtight container, preferably packed in strong moisture proof plastic bags and stored in a cool, dry place.

Equipment:

· Shelling machine
· Grinding mill
· Scales
· Heat sealer

7.3 Kashata

PRODUCT/PROCESS DESCRIPTION

Kashata (or peanut brittle) is a brown crisp snackfood made from melted sugar and groundnut grits.

Principles of Preservation and Methods of Processing

Preservation is achieved by heat, which destroys enzymes and contaminating micro-organisms, and by the low moisture content of the final product which inhibits recontamination. The product is hygroscopic and requires a moisture proof package for an expected shelf life of several weeks.

Process Flow Diagram

PROCESS

NOTES

Nuts in shell


Shelling

Shell by hand or by machine.

Store

Store in gunny sacks and well ventilated room; keep sacks on pallets off the ground. Protect from rodents and insects.

Sort

Discard mouldy and shrivelled nuts.

Clean

Remove dust using a winowing basket and pick out stones, stalks etc. by hand.

Roast

Dry roast the nuts on a metal sheet/pan.

Cool

Cool in air to room temp.

Dehusk

Dehusk the nuts by rubbing them in a winowing basket or tray.

Winnow

Use a winowing basket.

Break

Break/crush into smaller grits.

Sieve

Use a manual or powered mill and sugarsieve through a 2-4 cm sieve.

Melt

Gently stir contents, melt sugar to prevent burning.

Mix

Stir the groundnut grits into the melted sugar continuously, until well mixed.

Cool

Pour the mixture onto a flat tray to a depth of 1-2 cm and leave to cool. Mark out 2 cm squares or other shapes with a sharp knife while the mixture is still warm.

Break

When fully cooled, break the pieces along the markings.

Pack

Pack in polythene bags and then seal.

Store

Store in cool, dry place.

QUALITY CONTROL

Hygiene

The raw material and product remain dry throughout the process and hygiene problems are therefore less than for wet foods. However normal hygiene rules for safe food handling should be observed.

Raw Material Control

Groundnuts should be harvested when fully mature. If the nuts are left in the ground for too long after reaching maturity they lose flavour and colour. Early lifting before maturity produces shrivelled nuts that are difficult to process. The nuts should be dried in the field while in the shell, and then while still on the stalk, turned upside down. Drying groundnuts on iron sheets or a roof is not recommended because the nuts become baked and lose their flavour.

Process Control

It is very important to shell the nuts before storing and to dry them thoroughly to prevent mould growth beneath the shell. Some moulds produce 'aflatoxin', a poison which is highly dangerous. Shells, stones and leaves, shrivelled or mouldy nuts should all be removed. The quality of the groundnuts in the final product is mostly determined by the time and temperature of hearing (roasting) and the size and moisture content of the nuts. The colour and texture of the final product is determined by the degree of heating of the sugar and the ratio of nuts: sugar.

Product Control

The main quality factors are colour, texture (hardness) and flavour of the product. The colour depends on the amount of heating of the sugar, the hardness depends both on the amount of heating of the sugar and the size and amount of groundnut grits added to the mixture.

PACKAGING AND STORAGE

The crispness of the product is maintained by packaging in sealed, strong moisture proof plastic bags and storing in a cool, dry place.

· Shelling machine
· Grinding mill
· Scales
· Heat sealer
· Sieve
· Roasting trays/pans

Equipment:


Figure 1 MILLING MACHINE

8.1 Gelatin

PRODUCT/PROCESS DESCRIPTION

Gelatin is a white/cream powder which can be used as a thickener or gelling agent for table jelly and a wide range of confectionary. It is also used to clarify wines. The shelf life is several months depending on the packaging and storage conditions.

Principles of Preservation and Methods of Processing

Heat is used to destroy enzymes and contaminating micro-organisms and recontamination is prevented by drying the product to a low moisture content. The process involves a hot water extraction of gelatin after it has been solubilised from the collagen in bones and tendons. After separation of the fat and meat solids, the gelatin is concentrated and dried and then ground to a fine powder.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Bones

Use fresh meat bones and tendons (e.g. legs, trotters or joints) as they contain more cartilagenous tissue.

Clean

Remove all meat from the bones by scraping. Retain cartilage tissues.

Size Reduction

Break bones into manageable pieces using choppers.

Heat/extraction

Boil gently for 5-6 hours.

Cool

Cool to room temperature.

Separation ® fat

Remove floating solidified fat.

Filter ® solids

Decant clear liquid to separate from layer of solids at the base.

Concentrate

Gently simmer to boil off water until the liquid is thick and viscous.

Dry

Sun dry in thin layers on metal sheets until clear and crisp.

Grind

Pound using a mortar and pestle or a manually operated mill to a fine powder. (this stage is optional as the gelatin can be sold as clear flakes).

Sieve

Sieve to a fine powder using a 0.5 mm sieve. This should be done quickly as the product is very hygroscopic.

Pack

Pack in sealed polythene bags.

Store

Store in a cool dry place.

QUALITY CONTROL

Hygiene

Bones should be fresh and without gross contamination by soils or bacteria. The long heating period sterilises the gelatin and normal hygienic food handling practices are sufficient to prevent recontamination before drying.

Raw Material Control

The yield of gelatin is determined by the amount of cartilage and the collagen in the bones. Bones that have a high collagen content (e.g. trotters, leg bones, joints) are therefore selected.

Process Control

Cleaning bones by scraping meat from them makes separation of the gelatin solution more easy. Breaking bones makes gelatin extraction more rapid and increases the yield. Hot water not only extracts the gelatin but also sterilises the product. The time and temperature of heating determines the yield of gelatin. Evaporation and drying should be done quickly to prevent microbial growth on the gelatin before it is fully dried. The thickness of the gelatin layer and the drying conditions mostly determine the drying time. The extent of grinding and sieving determines the fineness of the final product.

PACKAGING AND STORAGE

The product is hygroscopic and should be quickly packaged in moisture proof, clean containers such as plastic bags or metal containers. It should be stored in a cool dry place.

Equipment:

· Filter bags
· Grinding mill
· Heat sealer

8.2 Minced Meat

PRODUCT/PROCESS DESCRIPTION

Minced meat is fresh meat minced into small pieces and if desired, mixed with spices. It is used as a base for preparation of other meat products including meat balls and burgers. It should be bright red, with a soft texture and uniform sized pieces, free of excessive visible fat. There should be a faint odour of fresh meat.

Principles of Preservation and Methods of Processing

The temperature of the product is reduced by refrigeration to slow the actions of enzymes and contaminating micro-organisms. The shelf life is 1-3 days depending on the hygienic conditions during preparation and the storage conditions. The high risk of bacterial contamination on the finely divided meat and the need for refrigeration require expertise and strict control over hygiene. This is not therefore a suitable product for all small scale food processors - especially those beginning their first business.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Fresh meat


De-bone ® bone

Remove bones, tendons etc. by hand.

Separate ® fat

Remove most fat from meat.

Sort

Remove other unwanted parts.

Wash

Wash meat in cold water of good quality (boiled or cholorinated if necessary).

Mix

Add spices and/or salt as required.

Mince

Mince through a mincing machine fitted with a 3-5 mm diameter die.

Pack

Pack minced meat into plastic bags and tie or heat seal.

Store

Store in a refrigerator.

QUALITY CONTROL

Hygiene

It is essential that all tools, equipment and surfaces are thoroughly cleaned and sterilised before and after processing. Meat is very susceptible to microbial growth especially when finely divided, and strict personal hygiene and hygienic food handling practices should be enforced to prevent food poisoning bacteria from contaminating the product. Any spices used must be carefully prepared by a reputable company as these are often a source of food poisoning bacteria.

Raw Material Control

The meat should be freshly slaughtered, free from disease and handled carefully to prevent contamination. It should be boned and trimmed of excess fat and tendons.

Process Control

The main control point is the uniformity of size in the minced product. This is controlled by the die aperture of the mincer.

Product Control

The quality factors are colour and size of the minced pieces. These are controlled by the freshness of the meat, the procedures used to remove fat and the ide aperture of the mincer.

PACKAGING AND STORAGE

Mincemeat is packaged in polythene bags and stored below 10° C in a refrigerator. It is essential that the temperature of storage is not allowed to fluctuate as this will allow bacteria to rapidly increase and cause spoilage and/or food poisoning. The shelf life should not exceed 1-3 days.

Equipment:

· Mincer
· Scales

8.3 Biltong

PRODUCT/PROCESS DESCRIPTION

Biltong is a strip of dried meat which is dark brown with a salty taste and a flexible rubbery texture. It is used as a snack or to accompany sadza (thick porridge). The expected shelf life is several months under correct storage conditions.

Principles of Preservation and Method of Processing

The principle of preservation is to inhibit enzyme and microbial action by addition of salt to the surface of the meat and removal of moisture by drying.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Fresh Meat

Meat must be kept cool and should be protected from flies. It should be handled in a hygienic way to protect it from dust and dirt.

Separate ® fat

Remove as much fat as possible by hand.

Slice

Slice meat into uniform sized strips 20-25 cm in length, 2 cm wide and 1 cm thick.

Salt ¬ salt/spices

Rub salt into the meat slices. (500 g salt per 10 kg sliced meat). Spices and flavourings can be mixed into the salt if required.

Dry

Hook one slice of meat onto each hook and hang the hooks on hanging wire (Fig. 1). Sun dry the meat for 7-10 days depending on the climate. Enclose in netting/gauze to protect from flies.

Pack

Pack in polythene bags and heat seal.

Store

Store in cool dry conditions away from sunlight

QUALITY CONTROL

Hygiene

It is essential that all tools, equipment and surfaces are thoroughly cleaned and sterilised before and after processing. Strict personal hygiene and hygienic food handling practices should be enforced to prevent food poisoning bacteria from contaminating the product. The meat should be protected from insects and animals during drying.

Raw Material Control

The meat should be freshly slaughtered, free from disease and handled carefully to prevent contamination. Meat that can be easily cut into strips is best, but cheaper parts of the animal can also be used. Shin meat does not produce good biltong. The meat should be boned and trimmed of excess fat and tendons. Any spices used should be from a reputable supplier as these are often a major source of food poisoning bacteria.

Process Control

The main control points are 1) the size of the strips, which should be uniform to give similar drying times, 2) the drying rate which affects the product quality and moisture content and depends mostly on the climate and size of the strips, and 3) the amount of salt (and sometimes spices) rubbed into the meat which prevents surface bacterial growth during the initial stages of drying.

Product Control

The main quality factors are colour, taste and texture of the product. Colour and texture are determined by the drying conditions and taste is mostly determined by the amount of salt and spices used.

PACKAGING AND STORAGE

Biltong needs packaging to prevent contamination by dust, insects etc. and if transported to a more humid region, to prevent moisture uptake. If sold in the area of production a simple container of paper or cloth is sufficient to keep the product clean. Sealed polythene bags are suitable for transport and distribution to other areas. Biltong should be stored in a cool dry place away from sunlight to minimise rancidity and moisture uptake.

Equipment:

· Drying racks and mesh covers
· Heat sealer

8.4 Hamburgers

PRODUCT/PROCESS DESCRIPTION

A hamburger is a circular, flat pattie made from fresh mincemeat, often with the addition of spices, flour and/or egg. It has a dull red colour, a soft moist texture and a faint odour of fresh meat when sold fresh. The product is extremely susceptible to spoilage and great care is necessary to ensure that the storage temperature is maintained below 10° C in a refrigerator. The shelf life is 1-3 days at this temperature or up to 3 months when frozen. It may also be cooked before sale. The colour is then brown, the texture is firm and pliable and the odour is of cooked meat. The cooked product should not be cooled or frozen and should be sold within a few hours. It is essential that the cooked product is held at or above 60° C between cooking and consumption.

Principles of Preservation and Methods of Processing

In the fresh product the temperature is reduced by refrigeration to slow the actions of enzymes and contaminating micro-organisms. The shelf life is 1-3 days depending on the hygienic conditions during preparation and the storage conditions. The high risk of bacterial contamination on the finely divided meat and the need for refrigeration require expertise and strict control over hygiene. This is not therefore a suitable product for all small scale food processors - especially those beginning their first business. Preservation of the frozen product is by inhibition of enzyme and microbial action at the low temperature. The cooked product is preserved by heat, but as it remains moist it is easily recontaminated and therefore has a very short shelf life.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Minced Meat

From Section 8.2.

Mix ¬ salt
Mix ¬ flour
Mix ¬ spices

500 g minced meat, 1 teaspoon salt, 150 g flour, add spices for flavour. Mix all the ingredients into a homogeneous mass by hand, or more hygienically using a mixer.

Weigh

Weigh the mixture to portions of 100g.

Mould

Shape the portion in round flat shape, 8 cm diameter and 1 cm thick. A hamburger mould (or press) may by used to produce more uniform products.

Fry

Shallow fry in hot fat until brown to the centre.

Pack

Pack in small plastic bags.

Store

Store your hamburgers in a fridge or you save them hot

QUALITY CONTROL

Hygiene

It is essential that all tools, equipment and surfaces are thoroughly cleaned and sterilised before and after processing. Strict personal hygiene and hygienic food handling practices should be enforced to prevent food poisoning bacteria from contaminating the product.

Raw Material Control

The minced meat should be freshly prepared, free from disease and handled carefully to prevent contamination. It should be free of excess fat and tendons. Any spices used should be from a reputable supplier as these are often a major source of food poisoning bacteria.

Process Control

In the fresh product the main control point is the uniformity of size in the product. This is controlled by the size and shape of the burger mould. In the fried product the time and temperature of heating are additional control points.

PACKAGING AND STORAGE

The fresh product is packaged in polythene bags, often with a greaseproof paper liner between the burgers, and stored below 10° C in a refrigerator. It is essential that the temperature of storage is not allowed to fluctuate as this will allow bacteria to rapidly increase and cause spoilage and/or food poisoning.

Equipment:

· Mincer
· Burger mould
· Scales


Figure 1 HANGING WIRE

9.1 Kapenta (Dried Sardines)

PRODUCT/PROCESS DESCRIPTION

Kapenta are small (2.5 cm × 6 cm) dried silver fish which are sold intact. It has a typically fishy flavour and a salty taste and a hard leathery texture. It is used domestically with a main meal and as a component of animal feed formulations. The expected shelf life is several months under correct storage conditions.

Principles of Preservation and Method of Processing

The principle of preservation is to inhibit enzyme and microbial action by addition of acetic acid to the surface of the fish and removal of moisture by drying.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Fresh 'Kapenta'


Store

Use damp sacking over fish to keep evaporation low. Keep the fish in the shade out of direct sunlight. Ice can also be used. This helps to keep the fish wet and reduces the rate of micro-biological and chemical deterioration.

Clean

Remove weeds and snails by hand. The fish is left whole. Use clean water for washing away mud.

Acidify

Dip the fish in vinegar diluted with water (50% water: 50% vinegar).

Dry

Dry in the sun, turning at intervals.

Pack

Pack in plastic or jute sacks.

Store

Store in a well ventilated cool clean room.

QUALITY CONTROL

Hygiene

As the fresh fish is a low acid, moist food it is highly susceptible to microbial growth. This is more important with this product as it is not de-gutted and gut bacteria therefore remain in the product. It is therefore essential that all equipment and surfaces are thoroughly cleaned before processing. Strict personal hygiene and hygienic food handling practices should be enforced to prevent food poisoning bacteria from contaminating the product. The fish should be thoroughly dried to a low moisture content and should be protected from insects and animals during drying.

Raw Material Control

The fish should be freshly caught, free from disease and handled carefully to prevent contamination. It should appear shiny, metallic with a wet sheen. The eyes should be clear and projecting and the gills should be pink.

Process Control

The main control points are

1) the drying rate which affects the product quality and moisture content and depends mostly on the climate and size of the fish,

2) the amount of acetic acid used to prevent surface bacterial growth during the initial stages of drying.

Product Control

The main quality factors are colour, taste and texture of the product Colour and texture are determined by the drying conditions and taste is mostly determined by the freshness of the fish.

PACKAGING AND STORAGE

Kapenta needs packaging to prevent contamination by dust, insects etc. and if transported to a more humid region, to prevent moisture uptake. If sold in the area of production a simple container of paper or cloth is sufficient to keep the product clean. Sealed polythene bags are suitable for transport and distribution to other areas. The fish should be stored in a cool dry place away from sunlight to minimise rancidity and moisture uptake.

Equipment:

· No special equipment is required.

9.2 Fish Cakes

PRODUCT/PROCESS DESCRIPTION

Fried fish cakes are 3 cm diameter balls of fish meat, bound together with starch and egg and fried to a golden brown colour. They are sold for direct consumption as part of a meal or as part of a packed meal. They have a shelf life of less than 2 days when properly stored.

Principles of Preservation and Method of Processing

The principle of preservation is heat destruction of enzymes and micro-organisms during frying. The short shelf life does not require inhibition of spoilage micro-organisms during storage.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Fresh Fish

Any fish is suitable but larger fish have more flesh.

Store

The fish is kept under ice covered with a wet sack, or kept in cold water.

Mix ¬ water


Mix ¬salt


Heat

Boil in salted water for 5-10 min. depending on the fish size.

Separate ® bones

Separate by hand.

Heat

Cook the flesh thoroughly.

Mix

Mix 2 teacup sieved flour to 1 teacup of fish meat, add a pinch of salt, one egg and one tablespoon of sugar in a mixing bowl. Mix to a firm dough.

Form/Coat

Prepare mixture into 3 cm diameter balls and coat in flour.

Fry ¬ oil

Fry until the are cooked and golden brown. Check this by using a sterilised wire to ensure no material sticks to wire when removed from fish ball.

Cool

Cool on a wire tray to allow oil to drip. Sprinkle sugar or salt before packing.

Pack

Optional. If necessary, use sealed polythene bags or airtight containers.

QUALITY CONTROL

Hygiene

Heat during frying destroys most contaminating bacteria and the short shelf life restricts recontamination during storage. Good hygienic practices should be enforced during preparation of the mix to prevent gross contamination and possible survival of large numbers of bacteria after frying.

Raw Material Control

The main quality factors are the flavour, colour and particle size of the fish and freedom from bacterial contamination and insect damage. Other ingredients should be similarly fresh and wholesome. Oil used for frying should be clear, of good quality and free from rancidity. The quality characteristics of oil are described in more detail in Chapter 2 (Cooking Oils).

Process Control

The main control points are:

1) Accurate weighing and thorough mixing of ingredients, as even a small variation can cause large differences in the final product,

2) time and temperature of frying, which controls the colour, texture, flavour and moistness of the product.

Product Control

The main quality factors are colour, size/shape, aroma, texture and flavour of the product, and freedom from contamination and soils. Each is determined by the amounts and types of ingredients, control over mixing and frying stages. In particular the type and quality of the frying oil is a major influence on the product quality.

PACKAGING AND STORAGE

The product is eaten within a few hours and packaging is rarely necessary except to keep the product clean. The product should be kept at a temperature above 60° C to prevent bacterial growth if sold as a streetfood, or if to be reheated in the home, it should be stored in a cool, dry place away from sunlight which would accelerate rancidity of the oil in the product.

Equipment:

· No special equipment is required.

9.3 Smoked Fish

PRODUCT/PROCESS DESCRIPTION

Smoked bream is a dry, brown product that has a salty taste and a characteristic flavour. It has a shelf life of several months when stored correctly. It is a valuable product which has a high domestic demand.

Principles of Preservation and Method of Processing

The principles of preservation are as follows:

1) Heat from the smoke destroys enzymes and micro-organisms in the fish,

2) smoke deposits hydrocarbons on the surface of the fish which, together with the salt that is rubbed into the surface, inhibit microbial growth,

3) moisture is removed during smoking/drying and the low moisture content of the final product inhibits recontamination. The process involves rubbing salt into the prepared fish and smoking the fish until sufficient moisture has been removed.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Fresh fish


Clean

Clean the fish be removing sand, waste material and gills using clean water (Note: the removal of scale is optional), clean and wash with potable water.

Cut

Gut the fish from tail to head through the stomach using a sharp knife. The fish has to lie flat supported by the spinal cord. Avoid contaminating flesh with internal organs.

Salt

Place fish in salt water solution in several layers in container. Let it stand for 2 hours.

Smoke

Place the salted fish on the smoking racks orderly and not one on top of the other, with the back of the fish downwards. Allow the fish to lie on the rack away from flames, sprinkle fuel charcoal periodically on the wood chips. The fish must be kept 2-3 days on the rack with turning every 6 hours. Break the fish to test the dryness. It should break crisply when fully dried.

An enclosed house is preferable because it keeps the smoke inside. The fire should have a composition of 2/3 dry firewood and 1/3 freshwood to increase the smoke. The rack must be 2 meters above the fire.

Pack

Pack in jute/plastic bags or sacks.

Store

Store in a well ventilated room at a cool temperature.

QUALITY CONTROL

Hygiene

Fish is a low acid product that is extremely susceptible to bacterial spoilage and transfer of food poisoning micro-organisms when it is moist. It is therefore essential that all equipment and surfaces are thoroughly cleaned before processing. Strict personal hygiene and hygienic food handling practices should be enforced to prevent food poisoning bacteria from contaminating the product. The fish should be thoroughly dried to a low moisture content and should be protected from insects and animals during drying.

Raw Material Control

Fresh fish should have a shiny, metallic appearance, a firm texture and a fresh, seaweedy odour. Gills should be bright red and the eyes should be clear and protruding.

Process Control

The main control points are:

1) Adequate cleaning and preparation of the fish to prevent contamination of the final product,

2) correct smoking temperature and time; overheating causes excessive browning and underheating/inadequate time may result in incomplete drying and mould growth during storage.

Product Control

The main quality characteristics are colour, texture and flavour of the final product. These are each determined by the type of wood used to smoke the fish and the time/temperature of smoking.

PACKAGING AND STORAGE

Packaging is needed to prevent contamination by dust, insects etc. and if transported to a more humid region, to prevent moisture uptake. If sold in the area of production a simple container of paper or cloth is sufficient to keep the product clean. Sealed polythene bags are suitable for transport and distribution to other areas. The fish should be stored in a cool dry place away from sunlight to minimise rancidity and moisture uptake.

Equipment:

· A smokehouse can be made locally.

10.1 Cheddar Cheese

PRODUCT/PROCESS DESCRIPTION

Cheddar cheese is a firm solid compressed curd which has a pale yellow colour, a texture that varies from rubbery to flaky, a mildly acidic taste and a characteristic flavour/aroma. It has a shelf life of several days to several weeks depending on the storage conditions. It is used as an accompaniment to main meals, as a snack or in preparation of other foods.

Principles of Preservation and Methods of Processing

Cheese is preserved by a number of different mechanisms:

1) the raw milk is pasteurised to destroy most enzymes and contaminating bacteria,

2) fermentation by lactic acid bacteria increases the acidity which inhibits growth of pathogens and most spoilage bacteria and

3) the moisture content of the separated curds is reduced and salt is added, both of which inhibit recontamination.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Raw Milk


Pasteurise

Heat to 63° C for 30 min.

Cool

Cool with stirring, to 35-40° C.

Inoculate ¬ starter

Add 2% starter for faster acid production and less for a slower fermentation. Use an aluminum or stainless steel tub.

Mix ¬ rennet

Add prepared rennet (1% by weight of milk).

Incubate

Stop stirring and allow milk to stand (30 min.) until it sets to a firm curd.

Cut

Cut curd with spatula to determine if ready. Cut curd in cubes (8 mm). Rectangular stainless steel frames with nylon or stainless steel wire are available.

Stand

Stand for 5-10 min. for curd to firm.

Heat

Slowly increase temperature 1° C for each 7 1/2 min. up to 34° C and then finally to 38° C.

Stir

Stop stirring when half of the whey is removed.

Drain

Stir and drain until final whey is removed.

Cut

Cut into blocks 150 cm thick and turn them ever 14-20 min.

Cut

Cut into potato sized pieces using knives.

Mix ¬ salt

Add salt (approx 2% by weight).

Fill

Fill the required amount of curd into a cheesecloth (which was sterilized in hypochlorite), and place in the wooden cylinder of a cheese press.

Press

Apply pressure gently. Allow to stand for 30 min. Apply more pressure and press for 8 hours (usually overnight).

Pack

Remove from press, inspect, trim and package.

Store

Store at temp not exceeding 15° C. Leave to mature for 3 months.

QUALITY CONTROL

Hygiene

As milk is a low acid food that is very susceptible to spoilage and transfer of pathogenic bacteria to consumers, the methods used to handle milk at the dairy play an important role in determining the quality of the final product The main hygienic requirements are:

1) thoroughly clean and sterilise (with chlorine solution or boiling water) all equipment and utensils before and after processing (nb aluminium equipment should not be cleaned with chlorine solution),

2) strict enforcement of personal hygiene measures,

3) filter milk after milking to remove visable dirt and any 'ropiness',

4) cool milk immediately to control further growth of micro-organisms and enzyme activity.

Raw material control

The milk should be fresh and free of contamination by dust, dirt or other extraneous matter. Milk which is likely to contain antibiotics should not be used as they will inhibit the action of lactic acid bacteria.

Process Control

The main control points are

1) the temperature and time involved in heating and cooling the milk. Overheating and slow cooling causes changes to flavour, colour and nutritional value; underheating may result in inadequate destruction of enzymes and micro-organisms leading to contamination. The following control points affect the flavour and texture of the final product,

2) correct amount of rennet added,

3) incubation temperature to allow rapid production of lactic acid by the inoculated bacteria. If the temperature is too high the bacteria will be destroyed, if it is too low there may be insufficient acid production,

4) adequate cutting and draining of the curd to remove most of the whey,

5) correct time and temperature of cooking the curd,

6) correct amount of salt added,

7) correct time and pressure during pressing the curd.

Product Control

The main quality factors for cheese are the colour, taste and texture. The colour is determined mostly by the amount of heating during processing and the fat content of the milk. The taste and texture are both determined by the amount of lacic acid produced during the fermentation and this in turn depends on the amount of inoculum added to the milk and the temperature/time of incubation. The texture is further determined by the

PACKAGING AND STORAGE

Cheese does not require sophisticated packaging provided that the temperature is kept relatively low and it is not allowed to dry out. In a refrigerator the product may be wrapped in polythene. In a cool box the product requires protection against dust, insects etc. It should be stored in a cool place away from sunlight.

Equipment/materials:

· Cooler/refrigerator
· Thermometer
· Starter culture
· Cutting frame
· Cheese press

10.2 Yoghurt

PRODUCT/PROCESS DESCRIPTION

Set yoghurt is a smooth, firm, white gel with a characteristic acidic taste made by fermenting cow's milk. Other similar products can be made from goat's milk. It is used to accompany msima, as a dessert or as a dressing for vegetable salads. It has a shelf life of 3-8 days depending on the storage conditions.

Principles of Preservation and Methods of Processing

Preservation is achieved by

1) pasteurisation of raw milk to destroy contaminating micro-organisms,

2) acidification due to the production of lactic acid from lactose in the milk by added lactic acid bacteria,

3) storage at a low temperature to inhibit growth of micro-organisms.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Raw Milk


Mix

Mix homogenized milk (940g), skimmed milk powder (60g) for 1kg of product.

Heat

Heat to 70° C with a holding period of 20-30 mins.

Cool

Cool to 42-44° C (container dipped in tub containing cold water to accelerate the coding process).

Inoculate

Inoculate with selected strains of actively growing microbial stater culters (Lactobacilus, Bulgaricus and Streptocollus thermophilus).

Incubate

Maintain temperature of 42-44° C for approx. 5 hours until desired degree of acidity is achieved to correct consistency.

Cool

Cool rapidly to 8-10° C.

Store

Store in a cool place until next morning to check for curd formation.

Pack

Place lid in containers.

Store

Store in a cool place for 3-7 days depending on storage conditions.

QUALITY CONTROL

Hygiene and Raw Material Control

As milk is a low acid food that is very susceptible to spoilage and transfer of pathogenic bacteria to consumers, the methods used to handle milk at the dairy play an important role in determining the quality of the final product. The main hygienic requirements are:

1) thoroughly clean and sterilise (with chlorine solution or boiling water) all equipment and utensils before and after processing (nb aluminium equipment should not be cleaned with chlorine solution),

2) filter milk after milking to remove visible dirt and 'ropiness',

3) cool milk immediately to control further growth of micro-organisms and enzyme activity. Milk which is likely to contain antibodies should not be used as they will inhibit the action of lactic bacteria.

Process Control

The main control points are

1) the temperature and time involved in heating and cooling milk. Overheating and slow cooling causes changes in flavour, colour and nutritional value; underheating may result in inadequate destruction of enzymes and micro-organisms leading to contamination,

2) correct incubation temperature to allow rapid production of lactic acid by the inoculated bacteria. If the temperature is too high the bacteria will be destroyed, if it is too low there may be sufficient acid production to form the yoghurt.

Product Control

The main quality factors for yoghurt are the colour, taste and texture. The colour is determined mostly by the amount of heating during pasteurisation. The taste and texture are both determined by the amount of lactic acid produced during the fermentation and this in turn depends on the amount of inoculum added to the milk and the temperature/time of incubation.

PACKAGING AND STORAGE

The product may be sold in portions directly from the culture vessel, or alternatively the incoculated milk may be poured into pots and allowed to ferment in them. The whole pot plus the contents is then sold - either with a returnable pot or a disposable pot. In all cases the short shelf life of the yoghurt does not require sophisticated packaging and the product only requires protection against dust, insects etc. Pots should be stored in a cool place away from sunlight and preferably in a refrigerator.

Packaging Materials

Clay pots, gourds and wooden or ceramic bowls are each used traditionally and are suitable provided proper hygiene is overved in their preparation and cleaning, particularly if they are to be reused. Plastic yoghurt pots are becoming increasingly available and these are more hygienic, more attractive to customers, more convenient to use and easily sealed with a foil cover.

Equipment:

· Cooler/refrigerator
· Thermometer
· Starter culture
· Pot sealer (optional)

10.3 Fruit Yoghurt

PRODUCT/PROCESS DESCRIPTION

Fruit yoghurt is a semi-solid cultured milk which has a smooth creamy texture, a sweet-sour taste and the characteristic flavour and colour of the added fruit. It has a shelf life that is similar to traditional yoghurt (3-8 days depending on storage conditions) and is mainly used as a dessert.

Principles of Preservation and Methods of Processing

Preservation is achieved by

1) pasteurisation of raw milk and fruit pulp to destroy contaminating micro-organisms,

2) acidification due to the production of lactic acid from lactose in the milk by added lactic acid bacteria,

3) storage at a low temperature to inhibit growth of micro-organisms.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Fruit


Clean

Wash in clean water.

Peel

Remove peel, seeds etc. by hand.

Pulp

Pulp by hand or using a manual pulper (e.g. Fig. 1).

Pasteurise

Heat to 70-80° C for 15-20 min. with continuous stirring to prevent product burning onto the pot (temperature and time vary with different fruits).

Cool

Cool to room temperature.

Mix ¬ yoghurt (Section 10.2)

Mix with yoghurt according to taste (e.g. 1 part fruit to 3 parts yoghurt).

Pack

Pack in gourds, plastic yoghurt pots.

Store

Store in a cool place, preferably in a refrigerator, away from sunlight.

QUALITY CONTROL

Hygiene and Raw Material Control

As milk is a low acid food that is very susceptible to spoilage and transfer of pathogenic bacteria to consumers, the methods used to handle milk at the dairy play an important role in determining the quality of the final product and are described in detail in Section 10.2. Fruit used to produce the fruit base should be ripe or slightly over-ripe, free from insect damage or mould/yeast growth, and free from bruises, cuts or splits.

Process Control

The main control points for milk processing are described in Section 10.1. The main control points for processing of the fruit base are

1) correct sorting, cleaning and peeling to remove unwanted parts of the fruit and contaminants,

2) correct pulping to produce a uniform fine pulp without large pieces that would be inadequately heated during pasteurisation,

3) adequate time and temperature of pasteurisation to destroy contaminating micro-organisms (especially yeasts that are able to grow under the acidic conditions in the yoghurt),

4) mixing of pulp and yoghurt in the correct proportions to retain the thick creamy consistency while giving the correct flavour and colour to the final product.

Product Control

The main quality factors for yoghurt are the colour, taste and texture. The colour is determined mostly by the type and amount of added fruit. The taste and texture are determined by both the amount of lactic acid produced during the fermentation (which in turn depends on the amount of inoculum added to the milk and the temperature/time of incubation) and the type and amount of added fruit.

PACKAGING AND STORAGE

The short shelf life of the fruit yoghurt does not require sophisticated packaging and the product only requires protection against dust, insects etc. Although clay pots, gourds and wooden or ceramic bowls are each used traditionally, plastic yoghurt pots are becoming increasingly available and are more hygienic, more attractive to consumers, more convenient to use and easily sealed with a foil cover. The fill weight should be controlled to that indicated on the label. Pots should be stored in a cool place away from sunlight and preferably in a refrigerator.

Equipment/Materials:

· Cooler/refrigerator
· Thermometer
· Starter culture
· Pot sealer (optional)
· Fruit pulper
· Scales

10.4 Soured Milk

PRODUCT/PROCESS DESCRIPTION

Traditional soured milk is a thick clotted milk which possesses a stronger flavour and a more acidic taste than yoghurt. It has a similar shelf life of 3-8 days and is used as a drink or as an accompaniment to nsima.

Principles of Preservation and Methods of Processing

Preservation is due to the production of lactic acid by naturally occurring bacteria in the untreated milk. The high levels of acid inhibit the growth of spoilage bacteria and pathogens that may be present in the raw milk.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Raw Milk


Fermentation

Allow the milk to sour by naturally occurring bacteria in 5 Itr plastic containers fitted with lids. Place in warm ventilated room for 1-2 days.

Store

Store in a cool place.

QUALITY CONTROL

Hygiene

As milk is a low acid food that is very susceptible to spoilage and transfer of pathogenic bacteria to consumers, the methods used to handle milk at the dairy play an important role in determining the quality of the final product. The main hygienic requirements are:

1) thoroughly clean and sterilise (with chlorine solution or boiling water) all equipment and utensils before and after processing (nb aluminium equipment should not be cleaned with chlorine solution). This is particularly important as the raw milk is not heat treated and any contaminating bacteria will be retained in the product,

2) strict enforcement of personal hygiene measures,

3) filter milk after milking to remove visable dirt and any 'ropiness'. Milk which is likely to contain antibiotics should not be used as these will inhibit the action of lactic acid bacteria.

Process Control

The main control point is the correct incubation temperature to allow rapid production of lactic acid by naturally occurring lactic acid bacteria. If the temperature is too high the bacteria will be destroyed, if it is too low there may be insufficient acid production to form the yoghurt.

Product Control

The main quality factors are the colour, taste and texture of the cultured milk. The colour should remain unchanged during processing. The taste and texture are both determined by the amount of lactic acid produced during the fermentation and this in turn depends on the temperature/time of incubation.

PACKAGING AND STORAGE

The product may be sold in portions directly from the culture vessel, or alternatively the milk may be poured into pots and allowed to ferment in them. The whole pot plus contents is then sold - either with a returnable pot or a disposable pot. The product has a short shelf life and does not require sophisticated packaging - only protection against dust, insects etc. The product should be stored in a cool place away from sunlight and preferably in a refrigerator.

Packaging Materials

Clay pots, gourds and wooden or ceramic bowls are each used traditionally and are suitable provided proper hygiene is observed in their preparation and cleaning particularly if they are to be reused. Plastic yoghurt pots are becoming increasingly available and these are more hygienic, more attractive to consumers, more convenient to use and easily sealed with a foil cover.

Equipment:

· No special equipment required.

10.5 Butter

PRODUCT/PROCESS DESCRIPTION

Butter is a semi-solid emulsion containing approximately 80-85% milk fat and 15-20% water. It is white-yellow with a bland characteristic flavour and a slightly salty taste. It is a valuable product that has a high demand for domestic use and as an ingredient in other food processing (e.g. bakeries).

Principles of Preservation and Methods of Processing

The principles of preservation are

1) to destroy some enzymes and contaminating micro-organisms by pasteurising the milk,

2) to prevent microbial growth during storage by reducing the water content, by storing the product at low temperatures and by adding a small amount of salt to the aqueous phase of the emulsion during processing.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Raw milk


Pasteurise

Heat to 63° C for 30 min. to destroy most spoilage and pathogenic bacteria and some enzymes.

Heat

The milk is warmed to 36-40° C to optimise efficiency of cream separation.

Separate ® skim milk

Use a cream separator (Fig. 2).

Hold

The cream is held at 10° C for 10-12 min. to allow crystallisation of fat so that it can easily be churned into butter.

Churning

Chum in an enclosed vessel at approx. 60 rpm to form butter granules. It involves the following steps:



- fill the chum half full, to allow movement of the product in the drum,



- chum for five minutes and open briefly to remove excess air,



- chum until fat granules are evident and then remove liquid (buttermilk) that has separated from the fat granules,



- wash the granules in water (very clean and sterilised if necessary). Water equivalent to the weight of buttermilk is added,



- churning is continued until the butter granules are properly washed,



-1.5-2% salt is dissolved in water and the washwater is replaced by the salt water. Churning is continued for a further 5-10 min. at 30 rpm to compact the butter,



- remove the butter from the chum.

Form/pack

Make the butter into blocks by tapping/pressing with butter pats (Fig. 3). Greaseproof paper or plastic containers can be used. Normal pack sizes are a 50-250 g product

Storage

Butter is required to be stored in a cool place preferably a refrigerator to maintain a shelf life of several months. At room temperature it melts and gets rancid quickly especially if exposed to sunlight.

QUALITY CONTROL

Hygiene

As milk is a low acid food that is very susceptible to spoilage and transfer of pathogenic bacteria to consumers, the methods used to handle milk at the dairy play an important role in determining the quality of the final product.

The main hygienic requirements are:

1) thoroughly clean and sterilise (with chlorine solution or boiling water) all equipment and utensils before and after processing (nb aluminium equipment should not be cleaned with chlorine solution),

2) strict enforcement of personal hygiene measures,

3) filter milk after milking to remove visible dirt and any 'ropiness',

4) cool milk immediately to control further growth of micro-organisms and enzyme activity.

Raw Material Control

The correct storage control of cream is necessary to prevent deterioration and the consequent formation of rancid, unpleasant flavours in the final product. The cream should be stored away from sunlight in a cool place or refrigerator. The recommended temperature of storage is below 10° C. Water used for washing and salting the butter should be chlorinated or boiled to ensure that it is free from bacteria.

Process Control

The main quality control points in the process are:

1) Temperature control at 36-40°C during pre-heating milk before separation to optimise the efficiency of the separator. If the milk is too hot or too cold the milk fat will be difficult to separate and the yield of product will be reduced.

2) During churning of the cream it is important to observe the fat granulation in the chum because over-churning will result in oily butter and under-churning will result in a reduced yield. Experience and skill is needed to determine the cut point for production of butter granules.

3) Washing and salting is needed to remove buttermilk which would accelerate bacterial growth during storage and produce off-flavours and odours and affect the colour of the product. Salt must be well dissolved to prevent salt crystals in the product. The texture of the butter is adversely affected if it contains salt crystals or buttermilk.

PACKAGING AND STORAGE

Rancidity during storage is reduced by using clean, dry containers and by keeping the stored product away from light and heat in a cool place, preferably under refrigeration. Iron and copper should not be used in any vessels, utensils or packaging as these metals promote rancidity in the product (see also Chapter 2 Oil Extraction).

Equipment:

· Butter chum
· Cream separator
· Butter pats
· Thermometer

10.6 Ghee

PRODUCT/PROCESS DESCRIPTION

Ghee is a clear golden brown oil with a characteristic flavour of milk fat. It has a high demand for domestic use, as an ingredient for local food products (for example bakeries, confectionary manufacturers) and as an export commodity.

Principles of Preservation and Methods of Processing

The principles of preservation are:

1) to destroy enzymes and contaminating micro-organisms by heat and

2) to remove water from the oil to prevent microbial growth during storage. Ghee has a long shelf life due to its low moisture content. Storage over long periods requires an airtight, lightproof and moistureproof container and a cool storage room to slow down chemical deterioration (rancidity).

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Fresh milk


Pre-heat

Heat in an aluminum pan to 36-40° C to facilitate easy separation of fat.

Separation ® skim milk

Preheated milk is separated into cream and skim milk using a manual separator.

Heat

The separated cream is boiled in a vessel to evaporate water. During boiling the product is stirred continuously until the milk proteins start to coagulate and the cream changes from white to golden brown. After the heating is stopped and the product is left to set, all the particles settle at the bottom of the vessel. Skill is needed to determine the end point of boiling.

Cool

The product is left to cool so that it can easily be filtered.

Filter

The product is filtered very carefully using a cheese cloth so that it is clear without any particles.

Pack

Metal containers are normally used. They should be thoroughly cleaned, especially if they are reuseable, and they should be made airtight. Alternatives to metal cans include coloured glass jars with metal lids or ceramic pots sealed with cork/plastic stoppers.

Store

Store at room temperature away from heat and sunlight. The shelf life can exceed 12 months with proper packaging and storage conditions.

QUALITY CONTROL

Hygiene

As milk is a low acid food that is very susceptible to spoilage and transfer of pathogenic bacteria to consumers, the methods used to handle milk at the dairy play an important role in determining the quality of the final product

The main hygienic requirements are:

1) thoroughly clean and sterilise (with chlorine solution or boiling water) all equipment and utensils before and after processing (nb aluminium equipment should not be cleaned with chlorine solution),

2) strict enforcement of personal hygiene measures,

3) filter milk after milking to remove visible dirt and any 'ropiness',

4) cool milk immediately to control further growth of micro-organisms and enzyme activity.

However the heat treatment during processing and the low water activity of the ghee reduce the risk of bacterial spoilage and food poisoning. After heating normal hygienic food handling techniques should be used. Filter cloths should be boiled each day and thoroughly cleaned of particles to avoid contaminating the product

Raw Material Control

The milk used for ghee production should be fresh, good quality and free from dirt and excessive microbial contamination, so that it will not clot or curdle during processing. Older spoiled milk will impart an unpleasant flavour to the final product.

Process Control

The main quality control points in the process are:

1) Temperature control at 36-40° C during pre-heating milk before separation to optimise the efficiency of the separator. If the milk is too hot or too cold the milk fat will be difficult to separate and the yield of product will be reduced.

2) The end point of the boiling stage is shown by the correct colour and texture of the ghee. There is no simple test for this and it is judged by experience.

3) Correct filtering is essential to produce a clear product.

Product Control

The main quality factors for ghee are colour, clarity, flavour and odour. Correct colour and clarity are mainly due to proper filtering. The taste, colour and odour are determined by the rime and temperature of hearing. Overheating produces a burnt taste and odour and a dark colour.

PACKAGING AND STORAGE

Rancidity during storage is reduced by using clean, dry containers and by keeping the stored product away from light and heat. Iron and copper should not be used in any vessels, utensils or packaging as these metals promote rancidity in the product (see also Chapter 2 Oil Extraction).

Equipment:

· Cream separator
· Cheesecloth
· Filler
· Thermometer

10.7 Pasteurised Milk

PRODUCT/PROCESS DESCRIPTION

Liquid milk has a high demand because of its nutritional value and pleasant flavour. Milk from cows has a creamy white appearance, that from goats and other animals has a yellower colour and a higher viscosity. Milk is sold universally for domestic consumption, for use with other products (e.g. tea, porridge) and for use by other processors (e.g. butter, cheese, yoghurt). For small scale processors this is a relatively difficult product to produce as the process requires careful control over hygiene, a relatively high capital expenditure and short distribution channels to good markets as the shelf life (at 3-5 days) is shorter than most products.

Principles of Preservation and Methods of Processing

The principle of preservation is the destruction of pathogenic and most spoilage bacteria and inactivation of most enzymes by heat during pasteurisation at 63° C for 30 minutes. This time and temperature combination is described by regulations in some countries and should be carefully adhered to.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Raw milk


Filter

Milk is immediately filtered, by use of filtering pads, soon after milking.

Cool

A surface cooler (Fig. 4) is used to cool the milk to stop further multiplication of micro-organisms in milk.

Pasteurise

Use batch pasteuriser (Fig. 5). Control of temperature and time is very important for correct pasteurisation to give expected shelf life. The vessel to be used should be fabricated from stainless steel or aluminium or bought locally from hardware shops. Milk should be heated with constant stirring to prevent the product overheating/burning at the bottom.

Cool

Cool quickly to temperature below 10° C. Cooling is done by placing the pan containing the hot product into another vessel which contains cold water. The product is stirred continuously until the temperature drops.

Pack

Pack into sterilised bottles and seal with sterile lids using a small filling and capping machine.

Store

Storage should be in either a cooler or a refrigerator at below 10° C. The milk should not be exposed to sunlight as this will heat it, promote rancidity of milk fat and destroy the vitamin riboflavin.

Transport

The transportation of milk from the storage room to the market should be in a refrigerated vehicle if the distance to be covered is long. But for a short distance which takes less than an hour's drive refrigeration is not necessary.

QUALITY CONTROL

Hygiene and Raw Material Control

As milk is a low acid food that is very susceptible to spoilage and transfer of pathogenic bacteria to consumers, the methods used to handle milk at the dairy play an important role in determining the quality of the final product.

The main hygienic requirements are:

1) thoroughly clean and sterilise (with chlorine solution or boiling water) all equipment and utensils before and after processing (nb aluminium equipment should not be cleaned with chlorine solution),

2) strict enforcement of personal hygiene measures,

3) filter milk after milking to remove visible dirt and any 'ropiness',

4) cool milk immediately to control further growth of micro-organisms and enzyme activity.

Process Control

The main control points are the temperature and time involved in heating and cooling the milk. Overheating and slow cooling causes changes to flavour, colour and nutritional value; underheating may result in inadequate destruction of enzymes and micro-organisms leading to a reduced shelf life and the risk of food poisoning.

PACKAGING AND STORAGE

During packaging the most important quality control check is to ensure that filling equipment, bottles and caps are thoroughly cleaned and sterilised to prevent recontamination of the heat treated milk. This is especially important if the bottles are reused. Bottle fill weights should be accurately controlled and storage temperatures should be controlled below 10° C.

Equipment:

· Filling machine
· Capping machine
· Bottle sterilising equipment
· Thermometer
· Filtering pads
· Milk cooler
· Refrigerator

10.8 Flavoured Milk

PRODUCT/PROCESS DESCRIPTION

Flavoured milk is a ready to drink product which is produced from skim milk, added sugar and natural flavours (e.g. banana, pineapple, orange, chocolate etc.).

Principles of Preservation and Methods of Processing

The principles of preservation are to destroy most enzymes and spoilage bacteria and all pathogenic bacteria by heat during pasteurisation at 63° C for 30 minutes. This time and temperature combination is described by regulations in some countries and should be carefully adhered to.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Fresh skimmed milk

from section 10.5 + 10.6.

Mix ¬ sugar

Sugar is added to the milk and thoroughly dissolved. The amount added is mainly determined by the sweetness required in the final product

Pasteurise

Use batch pasteuriser. Control of temperature and time is very important for correct pasteurisation to give expected shelf life. The vessel to be used should be fabricated from stainless steel or aluminium or bought locally from hardware shops. Milk should be heated with constant stirring to prevent the product overheating/burning at the bottom.

Cool

Cool quickly to temperature below 10° C. Cooling is done by placing the pan containing the hot product into another vessel which contains cold water. The product is stirred continuously until the temperature drops.

Mix ¬ flavour

This has to be done after pasteurisation, because the colour and flavour can easily deteriorate during the heating process. Flavours are usually supplied as concentrated essences and, with proper hygiene, will not re-contaminate the pasteurised milk with bacteria. Only food grade colours or natural fruit extracts can be used.

Pack

Pack into sterilised bottles and seal with sterile lids using a small filling and capping machine.

Store

Storage should be in either a cooler or a refrigerator at below 10° C. The milk should not be exposed to sunlight as this will heat it, promote rancidity of milk fat and destroy the vitamin riboflavin.

Transport

The transportation of milk from the storage room to the market should be in a refrigerated vehicle if the distance to be covered is long. But for a short distance which takes less than an hour's drive refrigeration is not necessary.

QUALITY CONTROL

Hygiene and Raw Material Control

As milk is a low acid food that is very susceptible to spoilage and transfer of pathogenic bacteria to consumers, the methods used to handle milk at the dairy play an important role in determining the quality of the final product

The main hygienic requirements are:

1) thoroughly clean and sterilise (with chlorine solution or boiling water) all equipment and utensils before and after processing (nb aluminium equipment should not be cleaned with chlorine solution),

2) strict enforcement of personal hygiene measures,

3) filter milk after milking to remove visible dirt and any 'ropiness',

4) cool milk immediately to control further growth of micro-organisms and enzyme activity.

Process Control

The main control points are the temperature and time involved in heating and cooling the milk. Overheating and slow cooling causes changes to flavour, colour and nutritional value; underheating may result in inadequate destruction of enzymes and micro-organisms leading to a reduced shelf life and the risk of food poisoning.

PACKAGING AND STORAGE

During packaging the most important quality control check is to ensure that filling equipment, bottles and caps are thoroughly cleaned and sterilised to prevent recontamination of the heat treated milk. This is especially important if the bottles are reused. Bottle fill weights should be accurately controlled and storage temperatures should be controlled below 10° C.

Equipment:

· Filling machine
· Capping machine
· Bottle sterilising equipment
· Thermometer
· Filtering pads
· Milk cooler
· Refrigerator


Figure 1 MANUAL PULPER


Figure 2 CREAM SEPARATOR


Figure 3 BUTTER PROCESSING EQUIPMENT


Figure 4 SURFACE COOLER


Figure 5 BATCH PASTEURISER

11.1 Beer

PRODUCT/PROCESS DESCRIPTION

Beer is a fermented beverage, which is made from sorghum, finger millet or rice. The colour of the product varies from whitish (rice beer) to reddish brown (sorghum and millet beer). The flavour reflects the raw material used and has a sweet, alcoholic taste. The shelf life of the product is relatively short at up to two weeks as it is not usually pasteurised after fermentation. It is possible to extend the shelf life to several months by bottling and pasteurisation.

Principles of Preservation and Method of Processing

Preservation is achieved by inactivation of enzymes and contaminating micro-organisms during boiling and by the relatively high levels of alcohol which inhibit the growth of many spoilage micro-organisms. The process involves preparation of the malted grain 'mash' and fermentation by yeasts to produce the alcohol.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Dried Grains

Sorghum, finger millet, rice.

Winnow

Husks and dust removed using a winnowing basket.

Wash

Washing removes adhered soils.

Germinate

For rice beer, paddy is used for germination to produce malt.

Dry

Sun drying 1-2 days.

Grind

Grinding should give fine flour to pass through 1 mm sieve. Grind by hand or powered milling machines.

Mix

Add malted flour.

Heat

Boil for 3-5 hours.

Cool

Cooling is important because starter (yeast) cannot act at high temperatures. Room temperature is recommended.

Mix

Add starter (2-10% by weight).

Ferment

Fermentation time depends on climate and type of starter and cereal. In hot climate 1-2 days, but in cold climate more that 3 days.

Filter

Filter to remove solids and produce a clear product.

Pack

Pack in gourds, bottles etc.

Store

Store in a cool place out of sunlight.

QUALITY CONTROL

Hygiene

Although the raw materials are sterilised by boiling, the wort is an excellent substrate for microbial growth. It is therefore essential that all equipment is thoroughly sterilised to prevent contaminating bacteria from competing with the added yeast and producing acid instead of alcohol. This can be done by cleaning with boiling water or with chlorine solution. Care is necessary to wash the equipment free of residual chlorine as this would interfere with the actions of the yeast.

Raw Material Control

Grains should be harvested when fully mature to maximise the carbohydrate content, and properly germinated (Chapter 4.1) to maximise amylase activity. Dried grains should be properly stored to prevent moisture pickup which would allow mould growth and reduce amylase activity.

Process Control

The main control points are:

1) correct germination of grains and thorough drying (see Chapter 4.1 Cereal Products),

2) proper grinding of the cereals to increase the surface area and maximise amylase activity,

3) adequate time and temperature of boiling to hydrolyse carbohydrates to sugars and thus make them more available for yeast action,

4) preparation of an active yeast inoculum and addition of the correct amount to the wort,

5) cooling the wort to an optimum temperature for yeast action. Too low and the fermentation time is extended and may spoil before the alcohol level is increased, too high and the yeast would be destroyed,

6) proper filtration to produce a clear product

Product Control

The main quality factors are colour, flavour and clarity of the beer. The colour and flavour are determined mostly by the extent of boiling of the mash and the flavour is also determined by the extent of yeast activity. The clarity of the final product is determined by the success of filtration.

PACKAGING AND STORAGE

Packaging is usually only required to contain the product for the relatively short shelf life and to prevent contamination by dust, insects etc. Cleaned glass or plastic bottles, gourds etc. are sufficient. For a longer shelf life it may be possible to pasteurise the bottled beer using the techniques and equipment described for fruit juices (Chapter 3). The product should be stored in a cool place away from direct sunlight.

Equipment:

· No special equipment is required.

11.2 Lubisi (Banana Beer)

PRODUCT/PROCESS DESCRIPTION

Lubisi is made from bananas of the Jamaican variety, mixed with sorghum flour and fermented to an orange, alcoholic beverage. It is sweet and slightly hazy with a shelf life of several days under correct storage conditions.

Principles of Preservation and Method of Processing

Preservation is achieved by inactivation of enzymes and contaminating micro-organisms during boiling and by the relatively high levels of alcohol which inhibit the growth of many spoilage micro-organisms. The process involves preparation of the banana juice, mixing with sorghum flour and fermentation by yeasts to produce the alcohol.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Ripe Banana


Peel

Peel by hand, if peels are not easily removed then the banana is not ripe enough.

Extract ® residue

Use grass to knead or squeeze the banana such that only clear juice is obtained. Residue will remain in the grasses.

Mix ¬ water

Mix 1:3 water: banana juice ratio. To make the total soluble solids low enough for the yeast to act.

Mix ¬ sorghum

Sorghum flour: banana juice ratio, 1:12. Stir the mixture well. Sorghum is used to improve flavour and color of the beer.

Ferment

Ferment in plastic container, covered by polythene bags or flat wood pushed down by heavy stone. Leave to ferment for 18-24 hours.

Filter

Filter the liquid by putting in a cotton cloth bag and squeeze by hand or in a press.

Pack

Package in 1 litre plastic bottles.

Store

Store in cool place away from sunlight.

QUALITY CONTROL

Hygiene

The raw materials are not sterilised by boiling and the wort is therefore an excellent substrate for microbial growth. It is therefore essential that proper hygienic procedures are followed and that all equipment is thoroughly sterilised to prevent contaminating bacteria from competing with the yeast and producing acid instead of alcohol. This can be done by cleaning with boiling water or with chlorine solution. Care is necessary to wash the equipment free of residual chlorine as this would interfere with the actions of the yeast.

Raw Material Control

Bananas should be harvested when fully ripe, to maximise the sugar content and flavour. Over-ripe bananas should not be used as they may impart off-flavours to the final product.

Process Control

The main control points are:

1) proper grinding of the cereals to increase the surface area and maximise amylase activity,

2) extraction of a high yield of banana juice without excessive browning or contamination by spoilage micro-organisms,

3) proper filtration to produce a clear product.

Product Control

The main quality factors are colour, flavour and clarity of the beer. The colour and flavour are determined mostly by the preparation of the banana/sorghum mixture. The clarity of the final product is determined by the success of filtration.

PACKAGING AND STORAGE

Packaging is usually only required to contain the product for the relatively short shelf life and to prevent contamination by dust, insects etc. Cleaned glass or plastic bottles, gourds etc. are sufficient. The product should be stored in a cool place away from direct sunlight.

Equipment:

· No special equipment is required.

11.3 Ulanzi (Bamboo Wine)

PRODUCT/PROCESS DESCRIPTION

Ulanzi is either fermented or unfermented (sweet ulanzi) bamboo sap, obtained by tapping young bamboo shoots during the rainy season. It is a clear, whitish beverage with a sweet/alcoholic taste and a shelf life of several days under correct storage conditions.

Principles of Preservation and Method of Processing

Preservation is achieved by the relatively high levels of alcohol which inhibit the growth of many spoilage micro-organisms. In some cases the product is pasteurised in bottles to destroy enzymes and contaminating micro-organisms and therefore increase the shelf life to several weeks. The process involves extraction of the bamboo sap and a natural fermentation by yeasts to produce the alcohol.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Growing bamboo shoots


Select Shoots

Choose 1 m tall bamboo shoots.

Cut

Cut 10-15 cm for the top.

Tap

A tapping tumbler can be made using the same bamboo. Remove the tapping top by knife every day by cutting a 3 mm slice off. The sap produces sweet ulanzi.

Mature

Ulanzi is made by aging in which alcohol is produced. It is usually done for 5-12 hours.

Pack

Use glass containers as ulanzi is corrosive to metal containers.

Pasteurise

Heat at 64° C - 72° C for 15 minutes.

Cool

Cool to room temperature.

Store

Store in a cool, dark place.

QUALITY CONTROL

Hygiene

The raw materials are not sterilised by boiling and the wort is an excellent substrate for microbial growth. It is therefore essential that proper hygienic procedures are followed and that all equipment is thoroughly sterilised to prevent contaminating bacteria from competing with the yeast and producing acid instead of alcohol. This can be done by cleaning with boiling water or with chlorine solution. Care is necessary to wash the equipment free of residual chlorine as this would interfere with the actions of the yeast.

Raw Material Control

Bamboo shoots should be young to achieve a high yield of sap. The growing tip is removed and a container fixed in place to collect the sap. The container should be clean to prevent contamination of the fresh sap which would impart off-flavours to the final product.

Process Control

The main control points are

1) extraction of a high yield of bamboo sap without excessive contamination by spoilage micro-organisms,

2) correct time and temperature to allow the natural fermentation to take place,

3) if pasteurised, the correct time and temperature to inactivate enzymes and yeast.

Product Control

The main quality factors are colour, flavour and clarity of the wine. These are determined mostly by the conditions used in collection of the sap and the extent of fermentation.

PACKAGING AND STORAGE

Packaging is usually only required to contain the product for the relatively short shelf life and to prevent contamination by dust, insects etc. Cleaned glass or plastic bottles, gourds etc. are sufficient. For a longer shelf life it is possible to pasteurise the bottled wine using the techniques and equipment described for fruit juices (Chapter 3). The product should be stored in a cool place away from direct sunlight.

Equipment:

· No special equipment is required (for the pasteurised product, see Chapter 3).

11.4 Togwa

PRODUCT/PROCESS DESCRIPTION

Togwa is a non-alcoholic beverage which is used as a refreshing, energy rich drink. It is made from sorghum, millet or rice and the colour of the product is determined by the raw materials used. All are slightly hazy, sweeter and more viscous than beer. Togwa has little or no alcohol to inhibit microbial growth during storage and the shelf life is therefore only a few days under proper storage conditions.

Principles of Preservation and Method of Processing

Preservation is achieved by destruction of enzymes and contaminating micro-organisms by heat during boiling.

PROCESS FLOW DIAGRAM

PROCESS

NOTES

Dried Grains


Winnow

Husk, dust, light grains and light parts are removed using a winnowing basket.

Wash

Wash thoroughly using cold water.

Dry

Sun drying for 10-12 hours.

Germinate

Germination is done in darkness; banana leaves, or large sheet of cloth can be used to cover grains.

Grind

Grind to a fine flour to pass 1 mm sieve. Grinding can be done by hand or powered mill.

Dry

Dry to a dry flour 2-5 hours in the sun.

Heat

Boil for 30 minutes to produce gruel.

Cool

Stirring is important to assist cooling and avoid hard top layer formation.

Heat

Heating should be done steadily to just below boiling to give time for the analyse to act.

Mature

Leave overnight to mature.

Filter

Filter through clean cloth.

Pack

Pack in plastic container (1 ltr).

QUALITY CONTROL

Hygiene

Although the raw materials are sterilised by boiling, the wort is an excellent substrate for microbial growth. It is therefore essential that all equipment is thoroughly sterilised to prevent contaminating bacteria from spoiling the Togwa after it has been boiled. This can be done by cleaning with boiling water or with chlorine solution.

Raw Material Control

Grains should be harvested when fully mature to maximise the carbohydrate content, and properly germinated (Section 4.1) to maximise amylase activity. Dried grains should be properly stored to prevent moisture pickup which would allow mould growth and reduce amylase activity.

Process Control

The main control points are:

1) correct germination of grains and thorough drying,

2) proper grinding of the cereals to increase the surface area and maximise amylase activity,

3) adequate time and temperature of boiling to hydrolyse carbohydrates to sugars.

Product Control

The main quality factors are colour, flavour and clarity of the beer. The colour and flavour are determined mostly by the extent of boiling of the mash. The clarity of the final product is determined by the success of filtration.

PACKAGING AND STORAGE

Packaging is only required to contain the product for the relatively short shelf life and to prevent contamination by dust, insects etc. Cleaned glass or plastic bottles, gourds etc. are sufficient. The product should be stored in a cool place away from direct sunlight.

Equipment:

· No special equipment is required.

List of Authors

Chapter 1 Dried Food

Mr. Peter Fellows
Food Technologist
Intermediate Technology Development Group
Myson House, Railway Terrace
Rugby CV21 3HT
United Kingdom

Chapter 2 Vegetable Oil Extraction

see above

Chapter 3 Fruit and Vegetable Products

see above

Chapter 4 Cereal Products

Ms. Estella Mbale
District Community Development Officer
Lilongwe
Malawi

Ms. Habiba N.Y. Mtinda
Women Appropriate Food Technologies
Community Development Department
P.O. Box 70032
Dar-es-Salaam
Tanzania

Mr. Anathaniel Lwaitama
Training Officer
Ministry of Agriculture and Livestock Development
Research and Training
P.O. Ilonga Kilosa
Morogoro
Tanzania

Chapter 5 Pulses

Ms. Namukolo Musonda
Food Technologist
Village Industry Services/UNIDO
P.O. Box 35500
Lusaka
Zambia

Chapter 6 Root Crops

Mr. Sungaunyolo Banda
Food Engineer
Intermediate Technology Development Group
Division
Box 1268
Lilongwe
Malawi

Ms. Stella Kankwamba
Women's Programme Officer
Lilongwe Agriculture Development
Box 259
Lilongwe
Malawi

Chapter 7 Nut Products

Ms. Beatrice V. Chisiza
Women's Programme Officer
Mzuzu Agriculture Development Division
Box 131
Mzuzu
Malawi

Chapter 8 Meat Products

Ms. Pamela Bvute
Home Economic Skills Trainer
Manicaland Development Association
Chitepo Adult Training Centre
Private Bag 7903
Mutare
Zimbabwe

Chapter 9 Fish Products

Ms. Patricia Ngwerume
Assistant Training and Project Officer
Association of Women's Club
P.O. Box 338
140 Samora Machel Avenue
Harare
Zimbabwe

Chapter 10 Dairy Products

Ms. Lombe Chitundu
Technical Officer
National Council for Scientific
Research
P.O. Box CH158
Chelstone
Lusaka
Zambia

Mr. Francis Mlotha
Regional Manager (Solwezi)
Small Industries Development
Organization (SIDO)
Kitwe Regional Office
P.O. Box 21318
Kitwe
Zambia

Chapter 11 Beverages

Mr. Nyangeli Engelbert Engelbert
Food Technologist
Tanzania Food and Nutrition Centre
P.O. Box 977
Dar-es-Salaam
Tanzania