Sorghum protein quality

This chapter sets out the role and importance of protein in human health, human protein requirements, and the measurement of food protein quality. Specifically, focus is given to the need to improve sorghum protein quality and the developments that have already taken place in this area are reviewed. Lastly, the improvements in sorghum protein quality achieved to date in the Biosorghum project are presented and on the basis of these data, the potential of biofortified sorghum to improve children s nutritional status is evaluated. 

Jood, S., Kapoor, A.C., and Singh, R. 1993b. Biological evaluation of protein quality of sorghum as insect infestation. Plant Foods Human Nutr. 43, 105-114. 

TABLE 2.5 Protein content, protein digestibility, lysine and leucine contents and PDCAASs of normal and improved protein quality lines of sorghum, compared to wheat, maize, barley, and pearl millet (data from several sources as indicated)... 

Table 2.5 compares the protein quality in terms of lysine, leucine, protein digestibility, and PDCAAS of different types of sorghum, including an early transgenic biofortified sorghum line and other major cereals ... 

Biofortified sorghum, developed using recombinant DNA technology, has substantially improved protein quality in terms of lysine content and wet-cooked protein digestibility compared to normal sorghum. 

MacLean, W. C., Jr., Lopez, de Romana, G., Placko, R. P., and Graham, G. C. (1981). Protein quality and digestibility of sorghum in preschool children balance studies and plasma free amino acids. /. Nutr. Ill, 128-136. 

Hamaker, B. R., and B. A. Bugusu. 2003. Overview Sorghum proteins and food quality. In Afripro workshop on the proteins of sorghum and millets Enhancing nutritional and junctional properties for Africa, ed. P. S. Belton and J. R. N. Taylor. Pretoria, South Africa, April l-A, 2003. 

Ford, J.E. and Hewitt, D, (1979). Protein quality in cereals and pulses. 3. Bioassays with rats and chickens on sorghum, barley and field beans. Influence of polyethylene glycol on digestibility of the protein in high tannin grain. J. 

A diet based exclusively on cereals only provides about 50% of the protein requirement for growing infants. The most limiting amino acid in all cereals is lysine (Chapter 17). The second limiting amino acid for maize is tryptophan, whereas it is threonine in the rest of cereals. The high-lysine cereal types of maize, sorghum, and barley possess better nutritional value due to improved protein quality or essential amino acid balance (Anonymous, 1988, Balaravi et al. 1976). 

Young, V., and PeUett, P. 1990. Human amino acid requirements with reference to protein quality. Pages 25-40 in Proc. Int. Conf. on Sorghum Nutritional Quality. Purdue University, USAID, and ICRISAT. West Lafayette, IN. 

Cereal grains, such as maize, barley, wheat and sorghum, are the main ingredients of poultry diets and usually provide 30-60% of the total AA requirements. Other sources of protein such as soybean meal and canola meal must be provided to ensure adequate amounts and a proper balance of essential AAs. The protein levels necessary to provide adequate intakes of essential AAs will depend on the feedstuffs used. Feedstuffs that contain high-quality proteins (i.e. with an AA pattern similar to the bird s needs) or mixtures of feedstuffs in which the AA pattern of one complements the pattern in another will meet the essential AA requirements at lower dietary protein levels than feedstuffs with a less desirable AA pattern. This is important if one of the goals is to minimize N excretion. 

Kissel and Yamazaki (209) studied the effects of lipid extracts from wheat flour and soy and safflower lecithins on improving cookie spread when the cookies were made from protein-fortified wheat flour. Soy lecithin was most effective, and it also improved the quality of cookies made from weak flours such as sorghum and millet (210). 

Continued research is needed to determine differences in composition, protein-binding, and enzyme inactivation properties of tannins from different sources. The mechanisms involved in the detoxification of polyphenols are not well understood. Simpler processing methods are required to improve the nutritional quality of high-polyphenol seed types. Sorghums, millets, and legumes provide the main subsistence of peoples in the under-developed countries. Any efforts to improve their nutritional quality may therefore be expected to alleviate the severe problem of malnutrition existing in this part of the world. 

TYPE OF DIET. A country s staple food is its primary source of carbohydrate, and for much of the poor population it must also serve as the principle source of protein. The degree to which this generally low-quality protein is supplemented by a more valuable or complementary source of protein (animal or legume protein) depends on income. The developing countries where wheat and rice are the principal crops have been the most successful in meeting food demand. In countries where corn is the chief crop, about 15% of the population is undernourished. In countries where the people subsist on millet and sorghum or root and tubers (much of Africa), some degree of malnutrition is virtually universal. 

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