ETHYL-SUBSTITUTED BETA-CASEIN - STUDY OF DIFFERENCES BETWEEN ESTERIFIED AND REDUCTIVELY ALKYLATED BETA-CASEIN DERIVATIVES

β-Casein carboxyl or amino groups were modified either by reaction with ethanol in acidic condition or by reaction with acetaldehyde via reductive alkylation at pH 8, respectively. Different degrees of esterification and alkylation were obtained. The extent of hydrolysis after 48 h of alkylated β-casein by α-chymotrypsin decreased, depending on the degree of alkylation. The conformation of alkylated β-casein was different from that of the native β-casein. Mean isoionic points for ester derivatives were 5.75, 7.80, 9.30, and 9.75 as compared to 5.30 for β-casein; those of alkyl derivatives were not significantly changed. Solubilities and emulsifying activities of ethyl-esterified β-casein were significantly lower than that of native β-casein. Solubilities of ethyl-alkylated β-casein were not significantly changed as compared to native β-casein, but their emulsifying activities were higher than that of native β-casein. © 1990, American Chemical Society. All rights reserved.