INFLUENCE OF KAPPA-CASEIN PHENOTYPE ON THE RENNET COAGULATION TIME OFBOVINE-MILK

Using individual milks from 6 pairs of cows differing in kappa-casein phenotype, we have investigated the effect of kappa-casein phenotype o n visual rennet coagulation properties. For this exercise we have adop ted the HOLTER-FOLTMANN linear relationship between rennet clotting ti me (RCT) and reciprocal chymosin concentration to provide a response s urface characteristic of each individual milk as a function of pH. Sig nificant differences in slope and intercept, attributable to genetic v ariations, were observed only near natural milk pH (6.70). kappa-BB mi lks had on average shorter RCT values than kappa-AA. Both phases of th e rennet coagulation reaction, proteolysis and aggregation, encompasse d by the RCT measurement, were influenced in the same direction by kap pa-casein phenotype.