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close this bookFood and Nutrition Bulletin Volume 06, Number 1, 1984 (UNU, 1984, 92 pages)
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View the documentAn old processing method, a new protein food
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An old processing method, a new protein food

S. Sefa-Dedeh
Department of Nutrition and Food Science, University of Ghana, Legon, Ghana

Traditional food processing methods play an important role in the processing and utilization of foods in Ghana and many other developing countries. Much of the food available on the market for direct use as ready-to-eat foods or food ingredients is processed using simple traditional technologies. Most of these technologies are based on local raw materials and equipment. It is unfortunate that the potential in using these simple, traditional methods for making high-protein foods has not been investigated fully. It is an alternative approach that merits careful consideration

The use of traditional food processing methods in developing high-protein foods has several advantages. For example, because the process will already be known by the people, problems associated with the correct application will be minimal. Equipment for the process may be available locally, thus eliminating the perennial problem of lack of foreign exchange for equipment purchase. If the application of simple, traditional technologies to the production of highprotein foods is successful, it will be easier to communicate information about the food to mothers, as is done in Mothercraft centres (1). The object will be the domestic and small-scale processing of high" protein foods.

In an attempt to find possible ways of increasing the utilization of grain legumes, I have suggested elsewhere the production of legume-based foods with physical and functional characteristics similar to an existing popular local food (2). The local food selected should enjoy a wide degree of acceptability, be convenient and ready-to-eat, and have a low moisture content for easy packing, storage, and transportation.

GARI-A VERSATILE READY-TO-EAT FOOD

A local food that possesses most of the characteristics described above is gari, a partially fermented, dehydrated meal prepared from cassava (Manihot utilissima Pohl) tubers. Gari used to be the traditional food among some segments of the Ghanian population. It is now widely used and accepted by most of the population, especially in the southern part of the country. It is in some of these areas that adequate protein is lacking in the diet, therefore any improvement in the protein content of gari or a gari-like product would be nutritionally beneficial.

Gari is a convenient, ready-to-eat, low-moisture product. The method used for making it from cassava tuber is very simple. A major drawback of the product is that it is basically a carbohydrate meal and thus of low nutritional quality if consumed by itself. Generally, it is eaten with other foods such as milk, fish, meat, vegetables, beans, and oil. This practice improves the nutritional quality of a gari diet. In cases where the product is consumed without much protein supplementation, problems generally as sociated with protein malnutrition may become manifest. Despite its inherent nutritional shortcoming, it is a popular food among some segments of the population. The product has interesting functional characteristics such as swelling in cold or hot water.

THE OLD PROCESSING METHOD

The process used for making gari involves small-scale grass-roots technology. The basic equipment and materials needed include sacks (generally made of cotton), heavy stones, a shallow iron pan, firewood, a cooking hearth, a sieve, a grater, a stirrer, and cassava tubers.

In a typical process the cassava is peeled, washed, and then grated to a wet meal. This is packed into cotton sacks and allowed to ferment for two to three days. During this period, heavy stones are placed on the sacks to press out water from the meal. It has been reported by Collard and Levi (3) that two stages can be identified during the fermentation of the cassava meal for gari manufacture. The first stage (first 24 hours) involves the production of organic acids from starch by Cornebacterium manihot The presence of organic acids leads to a decrease in pH and the hydrolysis of linamarin. The production of organic acids during the first stage stimulates the growth of the fungus Geotricum candida involved with the second stage. This fungus produces the aldehyde and esters responsible for the characteristic flavour of gari. After fermentation the resulting meal contains about 45 per cent water Figure 1 summarizes gari processing.



FIG. 1. Processing Steps in the Preparation of Gari

After fermentation, the cassava meal is sieved using a traditional cane sieve. After sieving, the "throughs" are dryroasted, a few at a time, in a shallow iron pan over moderate heat until dry and crisp. During roasting the fermented meal is stirred intermittently to prevent formation of lumps and to promote uniform heating. The heat reduces the moisture content through evaporation and cooks the cassava meal. The shape of the iron pan used for frying provides a good surface area for the moisture to evaporate. The moisture content of freshly dried gari is 3 to 5 per cent, but the product picks up moisture during storage, the amount depending on storage conditions.

NEW PROTEIN FOOD DEVELOPMENT

For the development of the new protein food, the product and process used for the old processing method described above were chosen. The selection of raw materials, process, and product characteristics were based on sociological, nutritional, economic considerations.

Sociological Considerations

The mixing of two food commodities in the preparation of meals is widely practiced in Ghana. This mixing of staples in a dish may be for one or more of the following reasons: - to achieve a certain acceptable product characteristic,

  • to provide good nutrition,
  • as a customary or cultural preference.

The use of cereal and legume mixtures as major ingredients in food preparation is not new to the Ghanian population. Cereal/legume mixtures used include rice and beans (boiled), corn and cowpeas as in apapransa, and the many forms in which corn and ground-nuts are mixed and used. It is expected that people already familiar with consuming foods in which two or more major staples are mixed may be more willing to accept a product based on this principle.

Nutritional Considerations

It is important that the product developed be made of ingredients that together provide protein of better quality. The raw materials selected were corn (Zea mays) and cowpeas ( Vigna unguiculata). Bressani and ElĂ­as (4) have shown that optimum protein quality for a mixture of corn and cowpeas is obtained when they are used in equal proportions in the diet. Orraca Tetteh (5) reported on the use of legumes as components of protein-rich foods for infants and toddlers in Ghana. He found that a food mixture made up of corn (60 per cent) and cowpeas (40 per cent) gave growth performance equal to 75 per cent of proprietary milk mixtures. In an effort to improve the nutrition of infants in particular and the general population as well, the two commodities corn and cowpeas will play significant roles. Although the current production levels of the two crops in Ghana are still below the national requirement, there is potential for increased production.

Economics

The process and the corresponding product developed should have economic advantages for the rural population and all who use them. This means, for example, that the inputs needed, i.e., equipment and raw materials, should be produced locally, thus eliminating foreign exchange problems. While contributing to improved nutrition, the process and product should provide monetary gains to the rural farmer, e.g., reduce losses caused by prolonged storage.

There are problems associated with the storage of cereals and grain legumes in Ghana that cause serious economic loss to the farmers. This is partly because of poor storage practices and the lack of simple processing methods to convert the grains into forms easily stored. It is thus thought that the processing of the legumes into acceptable products that can be stored easily will be one approach that will help curtail the excessive loss and deterioration associated with legume and cereal storage in Ghana. In addition, it is envisaged that a process to produce a marketable, easy-tohandle food using a method already known might stimulate the cultivation of corn and cowpeas. Increased production with its associated monetary gains may lead to increased consumption and therefore a general improvement of the protein nutrition of the population.

The Process

Figure 2 shows a typical process flow diagram. In this process, referred to as the Legon process, the cowpeas are dehulled and ground into flour. The corn is washed and steeped in water for 24 hours before it is ground. The corn and cowpea flours are mixed in the desired proportions and steamed in an exhaust box for 10 minutes. The steaming results in a lumpy mass that is broken up by stirring. This steamed mixture is dried with intermittent stirring in an earthenware washing bowl over low heat until dry and crisp. There have been various modifications in the process to make products with different functional characteristics, such as good cold or hot water absorption. The product is called abropa, meaning "good corn."

The major difference between the Legon process and other methods of preparing high-protein foods is the use of a simple, traditional drying method. It is the departure from the use of conventional drumdrying, spray-drying, and other forms of drying that require equipment and technology that may not be easily available in developing countries that makes the Legon process unique. The drying method used is basically the same as that for making gari. This means that the people who are already in the business of gari manufacture will not need to buy new equipment for making abropa.

PRODUCT CHARACTERISTICS

The product abropa prepared using the Legon process has an appearance very similar to that of gari. The product was described by some taste panelists as having a pleasant nutty flavour. When this product was compared to gari with respect to differences in particle size, crispness, colour, flavour, and taste, the panelists could not detect any differences between them. One of the ways in which gari is consumed in Ghana is to soak it in water, which the gari absorbs, and add milk and sugar to taste. In an attempt to find differences in consumer acceptance of gari and abropa, the samples were prepared in this manner and presented to panelists. All the abropa samples except one were rated as more acceptable than gari. Preliminary results from organoleptic evaluations were thus very encouraging.

All the abropa samples prepared have a low moisture content of about 4 per cent. This is an important characteristic for storing the product. If packaged in a good container it keeps very well. Gari, the traditional product whose characteristics were being simulated, has a protein content of about 1 per cent. The abropa samples prepared have protein contents ranging from 14 to 20 per cent, increasing according to the level of cowpea flour in the mixture. The samples containing skim milk powder in addition to cowpeas and corn had protein contents as high as 30 per cent. There is, therefore, great improvement in the protein content of the gari-like abropa.

This new protein food possesses good water absorption capacity and swelling characteristics, but it does not perform as well as gari. It is expected that modifications in sample treatment before drying will give products with better water absorption and swelling capabilities.



FIG. 2. Summary of the Legon Process for

Preparing Cereal/Legume Food

PRODUCT POTENTIAL

The preparation of a high-protein product with characteristics similar to an existing local popular food has been demonstrated. It is possible that, with little or no modication, the process may be applied to other cereal/legume combinations to produce convenient, dry, ready-to-eat foods.

Ghana, like most countries in Africa, has problems with infant feeding. Ready-to-eat nutritious weaning foods are not easily available, and there have been numerous calls for the development of weaning foods based on local raw materials. Abropa has potential as a possible weaning food. With its high protein content and ease of preparation, it could be a good vehicle for infant feeding. Abropa, because of its characteristics and method of preparation, will lend itself to vitamin and mineral supplementation. This is very important if the product is to be considered as a weaning food.

Just as gari is an important adult food in Ghana and other West African countries, abropa is likely to be acceptable if the desired functional characteristics can be achieved in the product. Depending on the initial treatments given to the raw materials, one can control the functional characteristics of the final product. The Legon process can thus be used to make products that can have varied functional characteristics and therefore provide a wide consumer acceptance.

ACKNOWLEDGEMENT

A research grant by the United Nations University to support this work under its Food, Nutrition, and Poverty Programme is gratefully acknowledged.

REFERENCES

1. G. G. Berggren, "Home-Prepared Food Supplements, Mothercraft Centres, and Nutrition in Haiti," Food and Nutr. Bull.,. 3 (4): 29 (1981).

2. S. Sefa-Dedeh. "Legume Research in the Next Decade, Expectations from a Hungry World," in preparation.

3. P. Collard and S. Levi, "A Two-Stage Fermentation of Cassava," Nature, 183: 620 (1959).

4. R. Bressani and L. G. Elias, "Legume Foods," in A. M. Altschul, ea., New Protein Foods, Food Science and Technology Series (Academic Press, New York, San Francisco, London, 1974), p. 230.

5. R. Orraca-Tetteh, "The Vital Role of Legumes in Human Nutrition," in W. G. Jaffe, ea., Nutritional Aspects of Common Beans and Other Legume Seeds as Animal and Human Foods (proceedings of a meeting held in Ribeirao Preto, Brazil, 1973).