The effects of storage temperature on postmortem changes in the contents of ATP and its related compounds were investigated in the adductor muscle, mantle, gill, and body trunk of the oyster Crassostrea gigas in relation to freshness. The K, K', and A. E. C. values taken for freshness indices were calculated from the contents of ATP and its related compounds.
In the adductor muscle, a marked decrease in ATP was observed together with the accumulation of AMP and IMP. The rates of ATP degradation during storage were on the order of 0>10>5°C storage. AdR was detectable only in the adductor muscle. In the other three tissues the level of AMP increased along with a slow decrease in the ATP level. The accumulation of IMP was not so marked as in the adductor muscle. The rates of ATP degradation during storage were on the order of 10>5>0°C storage in the body trunk, and 10>5=0°C storage in the mantle and gill. Although the K value remained low during the acceptable stage in all four tissues, the K' value in the adductor muscle and the A. E. C. value in the other three tissues changed rapidly and continuously from the beginning of storage at all storage temperatures examined (0, 5, 10, 15, and 25°C). The change rates of K' and A. E. C. values were higher at higher storage temperatures. The K' value obtained on the adductor muscle and A. E. C. values obtained on the other three tissues appeared to be useful as freshness indices for oysters.