[The effect of enzymatic modification on lysinoalanine formation in field-bean protein isolate and beta-casein]

Lysinoalanine (LAL) was determined in alkali-treated partial hydrolysates (PH) of casein, peptides isolated from these PH and in PH of field-bean protein to clarify whether intermolecular or intramolecular LAL bridges are preferentially formed. Furthermore, the formation of LAS in plasteins was studied as a contribution to plastein research. The formation of LAL in the peptide mixtures of beta-casein and the decrease of the LAL content in the PH (as compared to intact proteins) indicates that the formation of LAL favours the intramolecular cross-linking of polypeptide chains. The LAL content decreases as the degree of hydrolysis of the PH of the field-bean protein isolate increases, and depends upon the protease used in the production of the hydrolysates. The LAL contents of the alkali-treated plasteins are less than those of the initial hydrolysates. The decrease of the LAL content is directly proportional to the hydrolysis proceeding during the plastein reaction.