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 degrees 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 degrees 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 degrees C due to the inactivation of TGase. On the other hand, the addition of E-64, a cysteine protease inhibitor, suppressed completely and partially the formation of 150 kDa component at 25 and 55 degrees 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.