The effect of freezing and aldehydes on the interaction between fish myoglobin and myofibrillar proteins.

The interaction between fish myoglobin (Mb) and natural actomyosin (NAM) extracted from fresh and frozen fish was studied. The quantity of soluble Mb in Mb-NAM extracted was less in frozen than in fresh fish (P < 0.05). However, no differences were observed in Mb that remained in solution following preparation of Mb-NAM from frozen whole fish vs frozen fillets (P > 0.05). MetMb formation in Mb-NAM was generally greater than that observed in control Mb (P < 0.05); the greatest MetMb content occurred in Mb-NAM extracted from frozen whole fish (P < 0.05). The effect of different aldehyde oxidation products on the interaction between fish Mb and NAM was also studied in vitro. The loss of soluble Mb from NAM:Mb preparations was greater in the presence of hexenal and hexanal (P < 0.05) relative to controls, and the degree of solubility loss varied with aldehyde type. Hexenal caused greater OxyMb oxidation than hexanal (P < 0.05). Whiteness of washed NAM and NAM-Mb mixtures decreased following aldehyde addition (P < 0.05). In the absence of Mb, the Ca2+ -ATPase activity of NAM was lower with added hexenal than with hexanal (P < 0.05). However, no differences in Ca2+ -ATPase activity between hexanal and hexenal-treated samples were observed when Mb was present (P > 0.05). Reducing and nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses suggested that both disulfide and nondisulfide covalent linkages contributed to aldehyde-induced cross-linking between Mb and myofibrillar proteins.