Test procedures were developed for measuring the residual milk clotting activity of a protease produced by Endothia parasitica in curd and viii whey separated from freshly coagulated milk. A substrate was prepared by reconstituting 6 g low heat nonfat dry milk in 500 ml buffer containing 50 ml 0.5M cacodylic acid, 50 ml 0.2M CaCl2 , 30 ml 0.2M triethanolamine and 370 ml double distilled water. The substrate was stored at 2 to 4 C for 20 hours before use. Two milliliters of whey or supernatant from centrifuged curd-water slurries were inoculated into 25 ml of substrate at 30 C and the coagulation time noted, and compared with that produced by a known dilution of a standard enzyme solution. Endothia parasitica curd formed at pH 6.7 contained 45 per cent of the enzyme activity added to 454 g milk hut when formed at pH 5.2 the curd contained only 25 per cent. ix The recovery of Endothia parasitica protease in curd was made by preparing a 1:5 curd-water slurry, adjusting to pH 5.4, filtering and testing the filterate.

A procedure was developed for measuring residual rennin activity in curd extracts and whey. A sensitive substrate at pH 5.8 was prepared by mixing 6 grams of low-heat nonfat dry milk in 500 milliliters buffer containing 0.05 molar cacodylic acid, 0.02 molar calcium chloride, and 0.012 molar triethanolamine, and storing it at 2 degrees centigrade for 18 hours. Two milliliters of whey or curd extract were inoculated into 25 milliliters of substrate at 30 degrees centigrade. The coagulation time was measured and compared to that induced by 2 milliliters of a known rennin concentration added at the same time to identical substrate. Recovery of activity was determined by adjusting milk samples to pH 5.20 and coagulating them with a known concentration of rennin. The clot was broken by agitation and the curd separated from the whey by centrifugation. Activities accounted for in the curd and whey amounted to 91±1.6 per cent the activity added to the milk. Maximum release of activity from curd was achieved by diluting the curd 1:15 with water and adjusting the pH to 6.80. Inclusion of curd particles with the inoculum decreased the sensitivity of the substrate.