Influence of Endogenous Proteases and Transglutaminase on Thermal Gelation of Salted Squid Muscle Paste

ABSTRACT: Thermal gelation of salted squid mantle muscle paste was studied in relation to endogenous proteases and transglutaminase. Myosin in the paste was preferentially degraded into 130‐kDa and 90‐kDa fragments at an optimum temperature of 30 °C. Degradation was inhibited with EDTA or 1,10 phenanthroline, suggesting the presence of metalloproteases. Myosin degradation was markedly reduced above 40 °C. Although 10 mM Ca 2+ increased cross‐linking of myosin heavy chains by activating the endogenous transglutaminase, setting effect on thermal gelation of the paste was offset by degradation induced by simultaneously activated calpains. Ca2+ and the alpain inhibitor, E64, significantly improved the breaking strength and strain of thermal gels preincubated at 40 °C.