MILK-COAGULATING ENZYMES OF TUNA FISH WASTE AS A RENNET SUBSTITUTE

Extraction and activation of the tuna zymogen is influenced by tempera ture, pH, salt concentration and freshness of the stomach tissue. The presence of 25% NaCl in:the : extraction process markedly enhanced the yield of tuna gastric enzyme. The milk-coagulating time for both tuna :protease and rennet, at an incubation temperature of 32 degrees C, wa s dependent, at similar level, on the pH (5.5-6.4) of the milk as a su bstrate. Tuna protease was less sensitive to losses of activity than r ennet at pH values above 6.4. Both enzymes became unstable beyond pH 7 .0 and completely lost their activities at pH 8.0. The purpose of this study was to determine the best conditions for recovery of the fish e nzyme and to compare its behavior to that of rennet.