Proteolysis Affects Thermal Gelation of Squid Mantle Muscle

Thermal gelation of squid mantle muscle was studied by means of gel strength measurement and SDS-polyacrylamide gel electrophoresis. The gel strength of thermally induced squid meat gel decreased when squid meat paste was heated in two steps (35°C for 30 min followed by 90°C for 30 min). This decrease in gel strength was effectively depressed by the addition of protease inhibitors such as ethylenediaminetetraacetic acid (EDTA), phenylmethylsulfonyl fluoride (PMSF), and soybean trypsin inhibitor, indicating that me-tallo- and/or serine-proteases were mainly involved in the deterioration of squid meat gel prepared by two-step heating. SDS-PAGE analysis demonstrated that EDTA or PMSF suppressed the degradation of myosin heavy chain.