ABSTRACTMyosin heavy chain (MHC) content of cooked gels of pollock and croaker surimi decreased during preincubation (“setting”) at temperatures ranging from 4–50C. Decreases in MHC content were attributed to either nondisulfide covalent cross-linking or proteolysis. Depending upon which process dominated at a given temperature, formation of stronger or weaker gels occurred, respectively. Maximum production of cross-linked polymers occurred at the optimum setting temperatures, i.e., at 25C for pollock surimi and 40C for croaker surimi. Subsequent cooking of these set gels at 90C decreased the amount of cross-linked polymers formed at the optimum setting temperature. Addition of free lysine-HCl inhibited formation of cross-linked polymers of MHC during setting and the increase in cooked gel strength for both species. This supports published evidence that cross-linking of MHC during setting may be of the ε-amino-(γ-glutamyl) lysine I type, mediated by a transglutaminase enzyme.