Grain cereals amino acids

JM Concon. Chemical determination of critical amino acids in cereal grains and other foodstuffs. In M Friedman, ed. Protein Nutritional Quality of Foods and Feeds. Part 1 Assay Methods—Biological, Biochemical, and Chemical. New York Marcel Dekker, 1975, pp 311-379. 

Fig. 22.2 Main limiting indispensable amino acids of cereal grains (g/16 g N). Straight lines indicate requirements for chicks dotted lines indicate requirements for growing pigs.

Plant proteins from single sources, such as soybean meal, may be abundant in specific amino acids that are deficient in some cereal grains. Thus a combination of soybean meal and com with theh amino acid symbiosis may provide an exceUent amino acid profile for dogs. Plant protein mixtures alone do not meet the amino acid needs for cats, because taurine [107-35-7] is not generaUy present in plant proteins. 

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. 

Vitamins B6, B12, and folate An elevated plasma homocysteine level is associated with increased cardiovascular risk (see p. 263). Homocysteine, which is thought to be toxic to the vascular endothelium, is converted into harmless amino acids by the action of enzymes that require the B vitamins—folate, B6 (pyridoxine), and B12 (cobalamin). Ingesting foods rich in these vitamins can lower homocysteine levels and possibly decrease the risk of car diovascular disease. Folate and B6 are found in leafy green veg etables, whole grains, some fruits, and fortified breakfast cereals. B12 comes from animal food, for example, meat, fish, and eggs. 

Niacin is found in unrefined and enriched grains and cereal, milk, aid lean meats, especially liver. Limited quantities of niacin can also be obtained from the metabolism of tryptophan. [Note The pathway is inefficient in that only about 1 mg of nicotinic acid is formed from 60 mg of tryptophan. Further, tryptophan is metabolized to niacin orty when there is a relative abundance of the amino acid—that is, alter the needs for protein synthesis and energy production have been met]... 

Nutritive value of foods and feedstuffs depends to a large degree on protein level and quality, i.e., the relative amounts of the component amino acids compared to the requirements of the animal for various metabolic functions. The cereal grains are notoriously low in certain essential amino acids. Usually lysine is the first or second limiting amino acid. The grain of rye (Secale cereale L.) exhibits an amino acid profile superior to that of other cereal grains, especially wheat (1,2,3,4,5). Despite this fact, lysine is still the first limiting amino acid in rye in most instances (6,7). 

Reduced nitrogen retention was reported when chicks were fed rye diets (18). Supplementation of those diets with amino acids increased the retention of only the supplemented amino acids and not those contributed by the rye. These observations are compatible with the trypsin inhibitor hypothesis of other researchers (9,10). On the other hand, examination of the differences between endosperm and embryo and trypsin inhibitors of barley, wheat, and rye has revealed that, in contrast to certain trypsin inhibitors from leguminous seeds, those from the cereal grains appeared to be relatively weak, nonstoichiometric inhibitors of trypsin (19). 

Dietary protein sources differ widely in their proportions of the EAA. In general, complete proteins (those containing sufficient quantities of EAA) are of animal origin (e.g., meat, milk, and eggs). Plant proteins often lack one or more EAA. For example, gliadin (wheat protein) has insufficient amounts of lysine, and zein (com protein) is low in both lysine and tryptophan. Because plant proteins differ in their amino acid compositions, plant foods can provide a high-quality source of essential amino acids only if they are eaten in appropriate combinations. One such combination includes beans (low in methionine) and cereal grains (low in lysine). 

When the diastase of the malt has had time to act the mash is inoculated with a smaller special mash of rye and malt in which a pure culture of lactic acid bacteria (Bacillus delbruckii) is growing. The mash is now incubated for about sixteen hours at the proper temperature (ca. 50° C., 1220 F.). During this time the proteins of the grains are partially hydrolyzed and some lactic acid is formed. The liquor now contains largely sugars, resulting from the action of malt diastase on the starch, lactic acid, amino acids, and other hydrolysis products of the proteins, all in a highly assimilable form for the yeasts, and the cellulose residues from the cereals. 

Soybean proteins are widely used as food additives in European derived societies, primarily in processed foods, and this trend continues to grow annually. This makes soybean proteins a pervasive component of the human diet in industrialized countries. Solvent extracted soybean meal is also widely used as an animal feed additive (ref. 5, for review), because it is an inexpensive source of high quality protein that contains more of essential amino acids lysine and tryptophan than most cereal crops. Combined with corn, the other primary feed grain used in the United States, a ration can be assembled that is adequate in both sulfur amino acid and lysine contents, and provides a high protein diet that is well balanced for poultry and pigs. 

The main reason for the popularity of SBM is the unique composition of amino acids (AAs) that complements the AA compositions of many cereal grains. The excellent AA quality in SBM is also the reason why SBM is now increasingly being used in the pet-food industry. While SBM is by far the most popular soybean product in livestock diets, other products are also being used to a varying degree. These products include full-fat soybeans, soy protein concentrate (SPC), soy protein isolate (SPI) soy-... 

The seeds of legumes and cereal grains provide humans with an estimated 70 percent of their dietary protein requirements, but the proteins in these seeds are also deficient in certain essential amino acids. Researchers have examined the possibility of genetically engineering the genes that code for these proteins to alter their amino acid composition, but they are complex, multigene families. 

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