Assessing the end-point temperature of heated fish and shellfish meats

ABSTRACT: Attempts have been made to assess the end-point temperature (EPT) of heated fish and shellfish meats by using the coagulation method together with sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis and enzyme activity determination. Unfrozen and frozen fish and shellfish meats were heat-treated at different selected temperatures with 0, 15 or 30 min holding times. Proteins were extracted with NaCl solution. The coagulation method was able to determine EPT of heated fish and shellfish meats between 60 and 67°C. SDS-PAGE patterns of the filtrates from heated meats were closely related to the results of the coagulation method and enzyme activity determination. Two proteins responsible for producing coagulum of fish meat extracts seem to be lactate dehydrogenase (LDH) and glyceraldehyde phosphate dehydrogenase (GAPDH). End-point temperatures determined by these methods were not significantly different between unfrozen and frozen samples. On the contrary, a highly thermostable protein with a molecular mass of 35 kDa was detected in heated shellfish meats up to 108°C. In scallop adductor muscle, this highly thermostable protein was found to be the tropomyosin subunit from its amino acid composition and their partial sequences. Tropomyosin could be used as an EPT indicator up to 108°C for heated shellfish meats.