APPLICATION OF CAPILLARY ELECTROPHORESIS TO THE STUDY OF PROTEOLYSIS OF CASEINS

Capillary electrophoresis using a hydrophilically coated capillary and a low pH buffer containing urea has been used to follow the proteolyt ic action of plasmin and chymosin on isolated casein fractions, whole casein and individual milk samples selected on the basis of their gene tic variants. Several of the main casein breakdown products were ident ified. These included, among others, gamma(1)-casein (CN) A(1), gamma( 1)-CN A(2), gamma(1)-CN B, gamma(1)-CN C, gamma(2)-CN A, gamma(1)-CN A (3), gamma(2)-CN B, gamma(3)-CN A and gamma(3)-CN B, as well as proteo se peptones, arising from the action of plasmin on the different genet ic variants of beta-CN. alpha(s1)-I-CN and alpha(s1)-CN f(1-23) from a lpha(s1)-CN, and para-kappa-CN and caseinomacropeptide from kappa-CN p roduced by chymosin action were also separated. The knowledge of their migration times provided information on the extent and origin of case in hydrolysis in both milk and cheese, as found in samples of proteoly sed milk or fresh cheese.