Thermal Inactivation of Residual Milk Clotting Enzymes in Whey

Cheddar cheese whey from milk clotted with six milk clotting enzymes (Mucor rniebei, Mucor pusillus var Lindt, and Endothia parasitica proteases; calf rennet, porcine pepsin, and chymosin-free bovine pepsin) were adjusted from pH 5.2 to 7.0 prior to heating at 68.3 and 73.9 C for .25, .5, 1, 5, and 10 min. Enzyme activities were measured before and after heating. Mucor miebei protease was the most heat stable at all pH values followed by Mucor pusillus protease, calf rennet, bovine pepsin, Endotbia parasitica protease, and porcine pepsin. The heat stability of all enzymes increased with decreasing pH except Endotbia parasitica protease was most heat stable at pH 7.0.