|Small Scale Processing of Oilfruits and Oilseeds (GTZ, 1989, 100 p.)|
|2. Target Groups and Technologies|
|2.1 Family level|
In most societies, the family comprises the smallest economic unit. In developing countries, however, a family does not usually consist simply of husband, wife and their children. More often, a family includes other relatives (grandparents, grandchildren, cousins, etc.) or even close friends living in the same household. In islamic countries, a family might include a second or more wives and their children. In traditionally oriented societies, the extended family is still very important for the social identity of the individual.
Viewed from the point of oil processing, a family is defined here as a group of people living together in one household, ranging in numbers from one (exceptionally) up to 30, sharing common social and economic interests and usually having their meals together. Oil processing at this level of social aggregation primarily aims at subsistence needs, but also contributes to cash income.
In many areas of developing countries, oil fruits and oil seeds are available as a rawmaterial, and processes to prepare vegetable oil are known to the population. The modest needs for vegetable oil for the family pot are supplied by the women, following traditional methods of processing.
Next to the production of oil for the family, women also make products for sale on the local market to earn the money required to pay for their contributions to other family needs, such as the ingredients for the daily family pot. These are generally made up by some vegetables and spices and, when the money is available, by some (dried) fish or meat, all prepared into a sauce. This sauce is eaten as a relish, that accompanies the staple, which is based on a starchy food as a grain or a root crop.
When men produce an oilcrop that must be processed before marketing, the processing is generally not carried out at the family level. When sizable quantities are involved, the processing is carried out by specialized groups at the village level. This will be dealt with in the next chapter.
Below, a description is given of some traditional methods at family level to process oil palm fruit and oil seeds for food and cash income.
(see Flowsheet 1)
The semi-wild palms are mainly of the dura" variety. The aura fruit contains large nuts with a thick outer shell. Around the nut is a relatively thin layer of oilcontaining fruit pulp.
Flowsheet 1 Traditional Process for Oil Palm Fruit
Women search for fruits that have dropped out of the bunches from the trees or buy loose fruit at the market. Women do not climb palms and thus can only obtain bunches of fruit that have been cut by the men. Women can pay men to climb the trees and cut the bunches. Bunches have to be stripped to obtain the fruit.
The fruit can be more easily separated from the bunches after fermentation in a heap for 3-4 days. To facilitate the separation the bunches can be cut in small clusters before fermentation.
The fruit is cooked and subsequently pounded using mortar and pestle. When larger quantities are to be processed, in some areas, the fruit is pounded using a halved drum and a large number of pestles or the fruit is mashed by trampling with the feet in a pit. Men can assist with the stripping of the bunches and the mashing of the fruit. After crushing by pounding or trampling, the mass of fruit pulp and nuts is mixed with excess water. The nuts are washed free from pulp and are allowed to settle to the bottom. The fibres are then thoroughly washed with water and finally pressed out by hand to remove all oil and oil-containing cell material.
In some areas just the floating cream is collected, whereas in others all the liquid that remains after removal of the nuts is taken. This mass is transferred to a drum and boiled for a few hours. The palm oil at the top is skimmed off and finally purified and dried by heating in a separate pot. The remaining sludge is sometimes concentrated by boiling and used for food.
The nuts are spread on the ground and dried in the sun, after which they are cracked to obtain the kernel, traditionally by tapping between stones. The fibre is also dried and used as a combustible.
The required time reported for processing one drum (44 gallons or 2001), containing around 150 kg of palmfruit, is on the average 24 and 32 man working hours respectively for Benin and Gambia.
Oil recovery out of a drum varies between 9 kg for aura' oil palm fruit in Gambia, about 15 kg for aura fruit in other countries and as much as 20 kg for a aura! tenera (improved variety) mixture in Cameroon.
Traditionally, the fruit could be left to ferment for days, making the processing quite easy. However, this oil contains a high percentage of free fatty acids and has a sharp taste. It is therefore known as hard" oil.
Possibilities for improvement
In principle the traditional method for processing oil palm fruit is based on the separation of the oil-containing cell material from the nuts and the fibre followed by the extraction of the oil from the cells by prolonged cooking. This process has a limited oil recovery and requires much water and energy.
These drawbacks can only be overcome by changing to a process that uses practically no water but demands thorough preparation of the fruit, before the oil can be extracted with a hand press.
Since such a system requires much more investment than the traditional process, it is not a feasible proposition at the family level. Only at village level can the investments be justified either in the form of a service system, to be used by processors against a fee' or as an asset of a specialized informal or formal co-operative. Details of the processes are given under 2.2.1.
(see Flowsheet 2)
Flowsheet 2 Traditional (wet) Process for Processing Oil seeds (General Flowsheet)
1. With groundnuts, palm kernels and often with shea nuts.
2. By pounding, crushing between stones or a stone and an iron bar or by the service mill; fresh coconut is grated.
3. Groundnut paste is treated by stirring and addition of some water (12 %). Crushed palm kernels are cooked in excess water. Shea nut paste is treated by beating in air and washing of the cream or cooking in excess water.
4. Tunkusa and kuli-kuli for human consumption from groundnuts; animal feed from palm kernels and coconuts.
Groundnuts are almost exclusively processed in combination with the utilization of the residue for human consumption. In fact often the by-product, a kind of a snack, has to be understood to be the main product and the manufacturing of the groundnut oil only as part of the process.
In Ghana the following process was observed:
- decorticated groundnuts are roasted, treated by a rubbing
action and winnowed to remove the pellicles
- the nuts are crushed between stones, several times to obtain a fine paste
- this paste is stirred vigorously, while gradually adding some hot and/or cold water (about 10 % w/w)
- when the oil appears it is skimmed off and the mass formed into large balls and some more oil is pressed out by hand; the balls are called: tunkusa
- the tunkusa is subsequently processed into kuli-kuli, a ring or ball-shaped snack, prepared by frying products moulded out of tunkusa in groundnut oil. It can also be used as the main ingredient for groundnut soup".
For Burkina Faso, a similar process has been described.
A typical example has shown a recovery of 0.5 kg oil and 3.5 kg kuli-kuli (out of 3.8 kg tunkusa) from 4.0 kg of groundnuts; the production of the oil and tunkusa took 5 man working hours.
After cracking the palmnuts, the palm kernels can be separated out. Traditionally they are processed into an oil after roasting. The roasting makes the palm kernels brittle and more easy to crush by pounding. However, the quality of the oil deteriorates because of the temperature and the oil becomes dark coloured. After roasting the kernels are pounded. Then the pounded mass is mixed into excess water and boiled for hours, during which the oil is skimmed off. Finally the oil is dried by heating. 18 kg of palm kernels give I gallon or 4 kg of oil in about 12 man working hours.
The basic way to process fresh coconut is to cut the coconut lengthwise in half and to remove the white kernel or so-called 'meat'. The meat is first grated on a grating surface by hand then mixed with water and pressed out by hand or foot. This procedure is repeated several times. The coconut milk obtained is left to stand for a few hours to permit the separation into a supernating oil-containing cream and water. Subsequently the cream is collected and transferred into a cooking pot and heated under continuous stirring to dry the oil by boiling. The protein in the cream coagulates and dries. The oil is filtered. The residue can be eaten as a snack.
Also shea nuts are processed following a wet process. This process has been studied in Mali and includes:
- drying and roasting of the nuts - decorticating of the
- pounding of the shelled nuts into a liquid mass, that contains particles smaller than about 3 mm
- crushing of the mass into a very fine paste between stones or a stone and a metal bar
- in some areas the brown paste obtained is mixed into water, and air is brought in by beating, a cream appears; this cream is washed several times to remove all brown particles and transferred into a cooking pot; the cream is heated until the oil is collected at the top; the oil is skimmed off
- in other areas or later in the year the brown paste is mixed into boiling water and boiled for an hour, after which the oil is skimmed off; more water is added and boiling continued; finally, a second layer of oil is skimmed off
- by the next day the oil has hardened into a fat, and can be packed in leaves.
The time required for processing (grinding and oil extraction) of 12 kg shea kernels was found to be at least 18 man working hours, of which 14 hours were required for grinding. Generally, however, much more time is needed. Oil recoveries depend on the quality of the nuts and the skills of the women and can range from 20 % to more than 40 % on kernel weight. Normal yields have been reported to be between 20 and 30 %. In South Mali, recovery rates of 34 to 41 % have been reported recently.
Possibilities for improvement
Traditional methods make use of readily available utensils as a pounding mortar, crushing stones, calabashes and cooking pots. As they all apply water to assist the separation of the oil, these methods have in common that crushing of the seed into a very fine paste is essential. This stage is the most time consuming and exhausting one. This drawback of traditional methods can only be overcome by crushing using mechanical means. Such means, as motorized mills, require considerable investment and are only feasible at the village level. In fact they are already available in many villages in the form of so-called service mills".
The only way to avoid the use of a motorized mill is to change to a complete dry process using a hand press. During this process the seed is treated before pressing with care, by crushing into flakes, moistening and heating, in order to make the oil available so that it can easily be extracted by pressing.
The equipment to be used is unsophisticated and sturdy. However, investments required are only feasible at the village level. The process will be treated in detail under 2.2.2.