Enzyme-catalyzed Cross-linking and Degradation of Myosin Heavy Chain in Walleye Pollack Surimi Paste during Setting

Walleye pollack surimi paste was incubated (set) at 25, 35, 45, and 55°C in the presence of either transglutaminase (TGase) inhibitor or protease inhibitor. In the absence of inhibitors, cross-linking of myosin heavy chains and formation of 150 kDa component occurred at the same time during the incubation at 25°C. Inhibition of endogenous TGase resulted in complete suppression of myosin cross-linking, while it did not suppress the formation of 150 kDa component. The cross-linking was also depressed above 45°C due to the inactivation of TGase. On the other hand, the addition of E-64, a cysteine protease inhibitor, suppressed completelyand partially the formation of 150 kDa component at 25 and 55°C, respectively. Together with these results, the 150 kDa component might be a proteolytic fragment of myofibrillar proteins, possibly myosin. The proteolysis as well as the cross-linking of myosin during the setting affected the textural properties of final cooked gels.