COMPARATIVE ASSESSMENT OF PROXIMATE COMPOSITION OF COWPEA SEED
Processing of cowpeas and legumes in general is essential to make them nutritious, nontoxic, palatable and acceptable. The constraints to maximum
utilization of cowpeas can be overcome by appropriate processing technology. Processing can be classified into domestic and industrial techniques. The domestic processing techniques that are practiced in villages in developing countries include dehulling, grinding, soaking, germination, fermintation, addition of salts, wet and dry heat treatments, cooking and roasting. Theses processes can also be achieved in the food industry. The industrial processing techniques that are not common in the villages include canning, roasting, extrusion cooking, formation of protein concentrates and isolates and texturized vegtable proteins. Processing can further be divided into primary and secondary processes. Primary processes yield storable products to be used as and when required and include smoaking, dehulling, grinding and milling. Secondary processes are involved in the preparation of final consumer products from cowpeas and include various forms of heat treatment, such as boiling, steaming, cooking, alkaline treatment, roasting and deep fat frying (Uzogara et al. 1992).
The potential of cowpeas to contribute more to African or tropical diets has been investigated (IDRC, 1973) with an emphasis on reducing postharvest losses (Beucchat, 1983), on developing appropriate technologies to alleviate the heavy labor imputs required in many traditional preparations (Reichert et al. 1979; Hudda, 1983). Cowpeas were chosen as the source of nutrients because of their relatively high protein content and their amino acid profile, which is both
superior to and complementary to that of cereal grains (Dovlo et al. 1976; Rechie, 1985). Protein- energy malnutrition of infants is one of the major nutritional problems in the world. It is due to several causes including lack of weaning foods, the preparation of weaning foods with inadequate protein content, and to the use of foods too low in energy density to satisfy the needs of the growing infants (Oyus et al., 1985). A weaning food commonly used in Nigeria is composed largely of sorghum with limiled amount of dried–milk powder, usually in the ratio 5:1. Such mixtures have been shown to be poor in protein content and quality (Akinrele and Bassir, 1967; Oyeleke, 1977) Amore suitable weaning food has been prepared based on soybean and maize flour enriched with vitamins (Akinrele et al., 1970).
An attempt was made to improve the quality of the popular mixture by replacing part of the sorghum with cowpeas, Vigna unguiculatea, (Oyus et al., 1985). Cowpea is being successfully used in child-feeding programme (Ologhobo, 1983). In tropical Africa cowpeas are primarily used in the form of dry seed cooked as a pulse in large variety of dishes. Preference is for brown, white or cream seeds with a small eye and wrinkled or rough seed coat. In many areas of both West and East Africa the tender green leaves are cooked like spinach or as relish. Green beans or cut green pods are used as avegetable of secondary importance. Cowpeas are also grown for fodder, ground cover or green manure but to a much lesser extent than for pulse. Cowpea is practically never grown as a sole crop in Africa. In Asia the pulse uses of cowpeas are important primarily in the drier regions such as India where increasing amounts of crop are used in dhal. In South America cowpeas are grown mainly as pluse. In the USA dry seed is grown mainly in California and Western Texas, whereas green peas for canning and freezing (Rachie, 1985).
Worldwide cowpea production in 1981 was estimated at 2.27 million tonnes from 7.7 million hectares. Cowpeas are grown extensively in 16 African countries, with this continent producing two–thirds of the total. Two countries– Nigeria and Niger- prduce 850,000 t annually or 49.3 per cent of the world crop. The second–highest producing country is Brazil where 600,000 t of dry seeds or percent of the worldwide total was produced in 1981. Other major producers in Africa include Burkina Faso (95,000t), Ghana (57,000t), Kenya (48,000 t). Uganda (42,000t ), and Malawi (42,000 t). Tanzania, Senegal and Togo each produces annually from 20,000 ton to 20.000 ton. Current estimates of production vary widely according to source, but the statistics are probably conservative for example, Asian production, including that of long beans as a vegetable, may be under estimated by a factor of 10 or at a level of about 1 millon hectares, concentrated in India, Sirlanka, Burma, Bangladesh, Philippines, Indonesia, Thailand, Pakistan, Nepal, China and Malaysia. India alone is estimated to cultivate more than half or 500,000 ha for dry seed fodder, green pods and green manure. Similarly, production estimates may be low for Africa and the Western Hemisphere where cowpeas are traditionally included as associated crops in peasant – farming system. Thus, realistic production levels may approach or exceed 2.5 million tonnes of dry seeds on about 9 million hectares.
The only developed country producing large amounts of cowpeas is USA. (60.000 ton). Low yields are significant attribute of production estimates, particularly in Africa and Asia where 240-300 kg/ha are typical (K.O Rachie et al., 1985). In Sudan the yield is 1070 – 1190 kg /hectare