Wheat amino acid composition

Seven diets were constructed from purified natural ingredients obtained from either C3 (beet sugar, rice starch, cottonseed oil, wood cellulose, Australian Cohuna brand casein, soy protein or wheat gluten for protein) or C4 foodwebs (cane sugar, corn starch, com oil, processed corn bran for fiber, Kenya casein for protein) supplemented with appropriate amounts of vitamins and minerals (Ambrose and Norr 1993 Table 3a). The amino acid compositions of wheat gluten and soy protein differ significantly from that of casein (Ambrose and Norr 1993). 

Friedman (21) studied the effect of pH on the amino acid composition of wheat gluten. At pH 10.6 and above (65 C, 3 hours) no cystine was present. LAL increased with pH above 10.6. Lysine decreased over the same range of pH s, while serine and threonine contents dropped sharply at pH 13.9. Friedman concluded that cystine is most sensitive to alkali and that LAL will form most readily if lysine residues are in proximity to the dehydroalanine formed from cystine. Thus, he explained that different steric considerations may explain the different susceptibilities of wheat gluten, casein, and lactalbumin to LAL formation. 

H Wieser, A Modi, W Seilmeier, HD Belitz. High-performance liquid chromatography of gliadins from different wheat varieties amino acid composition and N-terminal amino acid sequence of components. Z Lebensm Unters Forsch 185 371-378, 1987. 

Comparative study of amino acid composition of commercial samples of a high-protein and a low protein and a low-protein wheat flour. Contribs. Boyce Thompson Inst., 18, 477 (1957). With R. H. Mandl. 

The amino acid composition of alkali-treated casein, lactal-bumin, and wheat gluten are given in Tables I-III. The results show that the following amino acids are destroyed to various extents under basic conditions threonine, serine, cystine, lysine, and arginine, and possibly also tyrosine and histidine. The losses of these amino acids is accompanied by the appearance of lysinoalanine and other ninhydrin-positive compounds. 

Effect of pH on amino acid composition of wheat gluten. Conditions 1% wheat gluten 65°C 3 hours. 

The amino acid composition of the potato lectin is unusual in a number of respects the most abundant amino acid is hydroxy-L-proline (the first lectin reported to contain this amino acid207), 11.5% of the residues are half-cystine (compare wheat-germ agglutinin, with 20% of... 

The amino acid compositions of the beta-amylase from sweet potato, soya bean, wheat, and malted sorghum have been determined, and are shown in Table XIII. These results may suggest that the beta-amylase from these different sources differs in structure. This is, perhaps, not surprising, but it should be noted that the sorghum amylase contained 9% of pentose, and the important, sulfiir-containing amino acid cysteine was not reported and the soya-bean enzyme still contained traces of aipba-amylase and phosphatase. The sequence of amino acids, or the three-dimensional structure of any... 

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). 

Also they differ in amino acid composition from the gluten proteins, possessing lower amounts of glutamic acid and more lysine. Unfortunately, because they are present in the wheat endosperm in minor proportions, their presence it is not enough to overcome the lack of lysine in wheat. Analysis of aneuploid stocks of the wheat variety Chinese Spring has revealed that the HMW albumins of 69,63,60, and 45 kDa are controlled by genes on the chromosome arms 4DL, 4AL, SAL and SDL respectively. 

At the present time there is no apparent explanation for the inhibition of the later stage of protein synthesis by wheat gluten, but this analysis suggests that the differences in response to these three dietary proteins involves more differences in amino acid composition and identifies the portion of the pathway which should be the subject of further research. 

Shoup, F.K., Pomeranz, Y., and Deyoe, C.W. Amino acid composition of wheat varieties and flours varying widely in bread-making potentialities. J. Food Sci. 31 94—101,1966. 

If these results can be relied on, it suggests that the different behavior of wheat and maize proteins may depend on differences in amino acid composition/structure of the functional proteins rather than differences in their relative proportions. How these differences might influence the Tg is an area that offers a challenge for future research. Of course. 

The nutritive value of a protein resides in its amino acid composition. Thus, if a protein provides all the amino acids in exactly the required amount, the protein will be used effectively. Egg protein contains 60% of the indispensable and semi-indispensable amino acids. In contrast, whole wheat proteins contain only 40% of the indispensable amino acids. Consequently, even if whole wheat protein is supplemented with lysine, which is almost completely lacking, it still provides less indispensable amino acids per gram of nitrogen than all egg protein. Thus, the efficiency of a protein depends not only on the actual indispensable amino acids it contains, but also on the proportion in which these amino acids occur [24-26]. 

Whenever the calculated biological value was compared to experimental determinations of the biological value, the two values were found to be extremely close. Such mathematical formulas are limited by the fact that the proteins are not all digested at equal rates. This difficulty has been overcome by estimating the amino acid composition not directly after total hydrolysis of the protein, but on the product of peptic and tryptic digestion of the protein. Such experiments have revealed that whereas the amino acids of the proteins contained in roast beef or wheat or peanut flour are readily available, the amino acids of cotton seed flour are not [27]. 

Several different protein derivatives from oilseeds (peanuts, almond, sunflower), cereals (corn, rice, oat), and a miscellany of other vegetable sources (potato, lupine, cottonseed, fava bean) have also been proposed for use in cosmetics. Nearly all these derivatives are hydrolysates, and as their amino acid composition is similar, they should not have any advantage over traditional wheat and soy protein derivatives. Corn proteins, rich in sulfur amino acids (Met+V2Cys > 5%), oat proteins, and almond proteins are the most useful in this group. 

When we look at the amino acid compositions of the proteins from starchy endosperm and aleurone layers (Sect. 2.1.2) we can get some indication as to how the different kinds of protein are distributed within the kernel (Table 2.6). In wheat, the aleurone layer protein is clearly different from that in the remainder of the endosperm, being extremely rich in arginine this could reflect a high globulin level. Rice aleurone grains, however, are rich in albumins [69]. 

Table 2.6. Amino acid composition of protein from starchy endosperm and aleurone grains of wheat cv. Manitoba...

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