Amino acids wheat gluten

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. 

PER is a method to metabolize or determine the quality of protein in foods. Quality is measured by the amount of usable protein and the growth resulting from it through an animal assay. Formerly, this method was used as the standard method for all protein quality analysis. However, there is some question as to whether or not it is a valid measurement. This is because PER does not account for the differences in amino acid requirements between humans and rats (Seligson and Mackey, 1984), nor does PER account for the protein needed for cell maintenance. Therefore, PER results often overestimate the requirements for some amino acids and underestimate others. Specifically, PER tends to underestimate the protein quality of lysine-deficient proteins such as wheat gluten (Hackler, 1977). 

Recently, limiting essential amino acids have been attached covalently to soy protein isolates (24) and wheat gluten (52) by the water-soluble... 

The percentage of D-enanticmers relative to the total amount of the amino acid residue can be calculated by the relation (D/DfL) x 100. D-Aspartic acid accounts for 30% of that residue (which is thus 60% racemized) in treated casein, Pranine-D, and wheat gluten. In these three proteins, 22-30% of the phenylalanine (an essential amino acid) is the D-enanticmer, and in wheat gluten, 26% of glutamic acid has been converted to the D-form. 

In previous papers, we have (a) reviewed elimination reactions of disulfide bonds in amino acids, peptides, and proteins under the influence of alkali (5) (b) analyzed factors that may operate during alkali-induced amino acid crosslinking and its prevention (6) (c) demonstrated inhibitory effects of certain amino acids and inorganic anions on lysinoalanine formation during alkali treatment of casein, soy protein, wheat gluten, and wool and on lanthionine formation in wool ( 7, 9) (d) demonstrated that... 

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. 

Lysinoalanine formation in casein, lactalbumin, and wheat gluten was measured at 65°C at various pH s for 3 hours. Factors that control the extent of formation of the unnatural amino acid lysinoalanine during food processing and thus the degree of crosslinking in structurally different proteins are discussed. 

Amino acids are not only the building blocks of proteins but also occur in the free form. Amino acids commonly found in proteins have the L-conflguration. Of these amino acids (Table 1), Asn was first discovered in asparagus in 1806, and Thr, the most recently discovered, was Isolated from the hydrolysates of fibrin in 1935. Most of them were Isolated from hydrolysates of various proteins. Glu, first obtained from wheat gluten hydrolysate in 1886, was found to be the most important taste component in sea tangle by Ikeda in 1908. Later, industrial production of MSG was undertaken to utilize it as a seasoner. 

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