Thermal Inactivation of Residual Milk Clotting Enzymes in Whey

Abstract

Cheddar cheese whey from milk clotted with six milk clotting enzymes (Mucor miehei, 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 73.9C for .25, .5, 1, 5, and 10min. Enzyme activities were measured before and after heating. Mucor miehei protease was the most heat stable at all pH values followed by Mucor pusillus protease, calf rennet, bovine pepsin, Endothia parasitica protease, and porcine pepsin. The heat stability of all enzymes increased with decreasing pH except Endothia parasitica protease was most heat stable at pH 7.0.Whey from cheese milk clotted with Mucor miehei protease was adjusted from pH 4.2 to 6.4 at .2 intervals of pH and subjected to high-temperature short-time pasteurization at 73.9, 76.6, and 79.5C for 25 s. Milk clotting activity was determined before and after pasteurization. All measurable activity was destroyed above pH 5.4 by pasteurization at 79.5C, above pH 5.8 at 76.6C, and above pH 6.0 at 73.9C.