Studies on Rigor-Mortis and Rigor Off in Fish

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1. Rigor-mortis progress in fishes was associated with ATP degradation and lactate accumulation, and its rate was accelerated at 0^ﾟC. At 0^ﾟC capacity of Ca^<2+> uptake in sarcoplasmic reticulum was lowered while intracellular Ca^<2+> concentration was increased. Therefore, myofibrillar Mg^<2+> -ATPase was activated, and ATP was decomposed rapidly and rigor-mortis progress was accelerated. 2. The influence of acclimated temperature on rigor-mortis was obvious. The larger the difference between acclimated temperature and storage temperature was, the faster the progress of rigor-mortis was. 3. In puffer under exercise cultivation and wild red sea bream, ATP was decomposed slowly and rigor-mortis was prolonged. 4. Three kinds of "arai" of carp were prepared and the physical property of "arai" was determined. Factor analysis showed that "arai" at 0^。C and 18^ﾟC treatments resembled each other and treatment at 49^ﾟC yielded different results. Scanning electron micrography showed less liped … More droplets on the surface of "arai" than that of untreated fish slices. Slight gaps between muscle fibers were observed in "arai". In "arai" of sea bass prepared at 49^ﾟC ATP was decreased remarkably and contraction was very strong. By washing, Fructose-1,6-diphosphate (FDP) was produced and accumulated. At 49^ﾟC FDP was metabolized to lactate, and supplied ATP was considered to be consumed as contraction energy. 5. The thaw-rigor was investigated in frozen red sea bream and carp muscles. The strongest contractions were observed at -1.6^ﾟC in red sea bream and at -1.1^ﾟC in carp. This may be due to the fact that the melting or freezing points in the muscles of sea-water fishes are lower than those in fresh-water fishs. 6. As the cause of rigor off and softening, the fragmentation of myfibril was considered. alpha-actinin was liberated and solubilized from Z-line by protease. Consequently, the structure of z-line became fragile and fragmentation of myofibril occurred. Decomposition of connectin and nebulin during early storage also caused the fragility of myofibril. Less