Gluten formation, wheat

Rye Proteins. While rye is the only European cereal able to completely replace wheat in bread, rye protein is not as effective as wheat protein. One reason for this is that as much as 80% of the protein in a rye sour dough is soluble compared with 10% of soluble protein in a wheat dough. One factor that inhibits the formation of a gluten-like complex is the 4-7% of pentosans present, which bind water and raise the viscosity of the dough. The crumb structure is then formed from the pentosans in combination with the starch. 

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. 

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... 

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. 

Glutenin and gliadin are the two principal proteins in wheat to which the formation of the gluten is due. 

The production of plant derived seasonings from acid hydrolyzed plant proteins is described elsewhere. Recently the acid hydrolysis of plant proteins (wheat gluten, soy protein, etc.) has been questioned especially in the US because of the potential formation of toxic side products. These side products, especially dichloropropanols are formed from plant fats contained in the raw material by the action of concentrated hydrochloric acid which is used in autoclaves at elevated temperatures for hydrolysis [4]. The cancerogenic effect of dichloropropanols has been proven in animal experiments. 

Proline is the second most abundant amino acid (13-18%) contained in wheat gluten, and plays a very in rtant role in flavor formation during food processing. A great deal of work has been carried out by Tressl et aL (5) on the volatile conponents generated in proline-specific Maillard reactions. The most abundant proline-specific Maillard reaction products arc 2,3-dihydro-IH-pyrrolizines. 

It was observed that the reacted mixture of WGH-G contained large amounts of dark colored products while the mixture fi om the reaction of DWGH with glucose contained only very small amounts of colored products. Investigation of this phenomena and the formation of volatile confounds fi om the WGH-G and DWGH-G systems demonstrated that the deamidation reaction of wheat gluten hydrolysates would increase the formation of aroma confounds and decrease the formation of brown color. 

A siinilar phenomenon is also observed with flours which have been preserved. When these are heated, we observe an increase of the acidity due in part to the decomposition of fatty materials, and in part to the formation of volatile adds at the expense of the sugar and the starchy substances. According to Marion and Monget, the addity of deteriorated flours comes espedally from the decomposition of the gluten by enz)rmes, a reaction which entails the appearance of an add substance. While fresh wheat contains from 0.004 to 0.023 per cent add, calculated in lactic add, the addity in spoiled flours varies from 0.14 to 0.5 per cent. The add content of deteriorated rye flour may reach 0.5 per cent, whereas the healthy product contains only 0.045... 

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