HEAT-INDUCED INTERACTIONS BETWEEN SERUM-ALBUMIN, IMMUNOGLOBULIN, AND KAPPA-CASEIN INHIBIT THE PRIMARY PHASE OF RENNETING

Skimmed bovine milk and casein micelles (in the presence and absence o f various concentrations of individual whey proteins) were heated at 8 0 degrees C for 30 min. Cloned chymosin was added to the cooled prepar ations and the enzyme-catalyzed hydrolysis of kappa-casein determined by measuring the formation of caseinomacropeptide. All of the whey pro teins tested caused an inhibition of the enzymatic reaction. Heating m icelles with individual whey proteins at temperatures as low as 60 deg rees C also inhibited both the rate and the extent of the kappa-casein hydrolysis. The results show that interactions between kappa-casein a nd immunoglobulin G and serum albumin, in addition to the well-documen ted interaction with beta-lactoglobulin, inhibit the primary phase of the renneting reaction.