Application of capillary electrophoresis to the study of proteolysis during ripening of Gouda-type cheese

Using capillary electrophoresis, protein degradation during ripening of Gouda-type cheese manufactured from fresh raw milk was studied. alpha(S0)-casein (CN) and alpha(S1)-CN degraded in the early stage of ripening (<28 days) so that more than 90% of these proteins were hydrolyzed by 84 day maturation, In contrast, 38, 67 and 84% of alpha(S2)-CN, beta A(1)-CN and beta A(2)-CN remained intact, respectively. Para-kappa-CN derived from kappa-CN by rennet action also slightly degraded. As ripening progressed, two main casein break down products appeared. From a comparison of the alpha(S0)-CN/alpha(S1)-CN ratio to that of the break down products, these were considered to be alpha(S0)-I-CN and alpha(S1)-I-CN (fragment 24 similar to 199 derived from alpha(S0)-CN and alpha(S1)-CN). High correlation coefficient between the alpha(S1)-I-CN/alpha(S1)-CN ratio and the maturation period (<70 days) which is considered to be a suitable parameter to judge the maturity of cheese was observed.