Effect of preheating temperature on the microstructure of walleye pollack surimi gels under the inhibition of the polymerisation and degradation of myosin heavy chain.

Background: The physical attribute of heat-induced gel texture is highly dependent on the microstructure of the gel. In this study the microstructures of walleye pollack surimi gels preheated at various temperatures with and without inhibitors (ethylenediamine-N,N,N',N'-tetraacetic acid, iodoacetamide and leupeptin) were observed with a natural scanning electron microscope.

Results: Without inhibitors, gels preheated at 30 °C showed a fine and uniform network structure together with the highest polymerisation of myosin heavy chain (MHC) and the highest gel strength. At 60 °C, gels exhibited a broken, disrupted and loose cluster-like structure together with the highest degradation of MHC and the lowest gel strength. Under the inhibition of polymerisation and degradation of MHC a fine network was observed up to 40 °C during preheating. However, after a second step of heating at 80 °C the microstructures were disrupted and resembled each other regardless of the preheating temperature.

Conclusion: Heat-induced gel formation is related to the polymerisation and degradation of MHC and the microstructure of the gel during preheating. Gelation occurred during setting even under the inhibitory condition, and the formation of covalent bonding by transglutaminase is not essential to the formation of a three-dimensional network during setting but is essential to the gel strength enhancement effect of setting by subsequent heating at 80 °C.