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 Ca2+ 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.