The lysine content of wheat gluten was increased up to fourfold after reaction of pepsin-hydrolyzed wheat gluten with N'-benzylidenelysine in the presence of l-ethyl-3-(3-dimethylaminopropyl)carbodiimide. Although partially acid-hydrolyzed gluten reacted with L-lysine hydrochloride, thus increasing the lysine content up to 20-fold, the available lysine determined by the dinitrobenzenesulfonate method and the liberated lysine by the pepsin pancreatin digestion method were low, 48 and 41 % , respectively. This result suggests formation of y-a, y e , and a-e isopeptide bonds. When a reversibly €-amino protected lysine, N'-benzylidenelysine, was used for binding, the available lysine content increased to 91 % . However, the liberated lysine value stayed the same, suggesting the possibility of y-a bond formation. When pepsin hydrolysis instead of acid was used for solubilization of gluten, the liberated lysine value was improved to 65% compared to 31 and 45% for egg and casein, respectively. The bound lysine residues in the pepsin-hydrolyzed gluten were readily digestible and available.

No abstract