Cereal high-lysine

Watson, S.A. and Yahl, K.R. 1967. Comparision of wet-milling properties of opaque-2 high-lysine com and normal com. Cereal Chem. 44, 488-498. 

The legumes have a high lysine content (7,32), which makes them an excellent complement to cereal proteins. Protein contents of pumpkin breads were 5,0, 5,6, 6,2 and 6,7% for loaves that had 0, 20, 35 and 50% Navy bean flour, respectively. 

Cereal proteins are only about 70 percent efficient for dietary replacement purposes. The reason is that cereal proteins are deficient in lysine, an essential amino acid for humans (see Amino Acid Synthesis in this section). Thus a diet based on one source of protein (e.g., corn) can lead to malnutrition. A partial solution to the problem has been the breeding of high-lysine corn. Other plant proteins, particularly those from pod seeds (e.g., peas and beans) are deficient in the sulfur-containing amino acids. A successful vegetarian diet will therefore be balanced in cereals and pod seeds. 

Cereals have low confenfs of essential amino acids, particularly lysine and tryptophan. In developing countries especially, this creates nutritional deficiencies for a large proportion of the population because a single cereal may account for a major part of the protein intake. In some countries (Central and South America and sub-Saharan Africa), people rely on maize as their principal food. In order to counter the problem, high-lysine mutants of maize have been identified. However, these mutants are associated with negative effects on yield and they have soft, chalky kernels that are susceptible to disease and insect damage. 

The proteins of different cereal flours vary in their amino acid composition (Table 15.10). Lysine content is low in all cereals. Methionine is also low, particularly in wheat, rye, barley, oats and corn. Both amino acids are significantly lower in flour than in muscle, egg or milk proteins. By breeding, attempts are being made to improve the content of all essential amino acids. This approach has been successful in the case of high-lysine barley and several corn cultivars. 

New and Improved Varieties of Grains. Some of the limitations in the protein quality of the most important cereal grains have been overcome by cross-breeding them with mutant varieties so as to obtain new hybrids which have higher contents of both lysine and protein. Fig. C-40 shows how the new high-lysine and high-protein varieties compare with some of the older, more common varieties of the major grains. 

Also see CEREAL GRAINS and CORN, section headed "High-Lysine Corn.")... 

The food value of rye is similar to wheat. It is a good source of starch (carbohydrates) and a fair source of protein. However, the protein, in terms of essential amino acids, falls short in lysine compared to high-quality proteins. Therefore, like wheat and the other cereal grains, lysine is the limiting amino acid. Of the vitamins, rye is devoid of vitamins A, C, and B-12. 

The most important role of animal protein is to correct the amino acid deficiencies of the cereal proteins, which supply about two-thirds of the total protein intake, and which are notably deficient in the amino acid, lysine. The latter deficiency can also be filled by soyhtean meal, fish, protein concentrates and isolates, synthetic lysine, or high-lysine com. But such products have neither the natural balance in amino acids nor the appetite appeal of animal protein. 

Explain the reason why quality protein or high-lysine maize is nutritionally superior compared to regular maize counterparts. Investigate how opaque-2 maize was transformed into quality protein maize. What other cereals have high-lysine types ... 

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). 

Explain why the development of high-lysine cereals can partially solve protein malnutrition problems around the world Which cereals have genotypes that contain high-protein quality ... 

Bressani, R. 1992. Nutritional value of high lysine maize in humans. Chapter 12 in Quality Protein Maize. E.T. Mertz (ed.). American Association of Cereal Chemists. St. Paul., MN. 

What are the potential advantages of using waxy or high-lysine cereals in monogastric and ruminant nutrition ... 

The grain or pulse forms of legumes have a high total protein content (20-26%) and can therefore be used as a natural supplement to cereals. Pulses are normally deficient in the essential amino acids methionine and cystine but contain enough lysine, whereas cereals are deficient in lysine but contain enough methionine and cystine. 

Characteristically, legume seeds are rich in protein and contain intermediate to high levels of lysine and threonine which are important in balancing the deficiencies of these essential amino acids in cereal diets. Certain legume proteins, such as soybean, also exhibit strong functional properties, especially water solubility, water and fat binding and emulsification. Thus soybean flours, protein concentrates and isolates have been used widely as nutritional supplements and functional ingredients in foods. 

The nutritional value of proteins (see p. 360) is decisively dependent on their essential amino acid content. Vegetable proteins—e.g., those from cereals—are low in lysine and methionine, while animal proteins contain all the amino acids in balanced proportions. As mentioned earlier, however, there are also plants that provide high-value protein. These include the soy bean, one of the plants that is supplied with NH3 by symbiotic N2 fixers (A). 

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