Effect of storage temperatures on accumulation of glycerylphosphorylcholine and decomposition of phosphatidylcholine in fish muscle during cold storage.

The accumulation rate of glycerylphosphorylcholine (GPC) in carp ordinary muscle at -20°C was significantly lower than the rates at 0 and -10°C. The rate at -10°C, on the contrary, was slightly higher than that at 0°C. In frozen fish, the accumulation of GPC proceeded more appreciably than the increase in K value. At these low temperatures the accumulation of GPC corresponded closely to the decomposition of phosphatidylcholine (PC). However, this was not the case at 40°C at which GPC decreased after an initial increase and the amounts of accumulated GPC were much less than expected from the amounts of decreased PC. In muscle suspensions of a pacific mackerel and a carp, bacteria decomposed not only GPC but PC without forming GPC at 37°C, pH 7.5. However, no bacterial decomposition was observed at 0°C for 10 days in pacific mackerel muscle. Consequently, the accumulation rate of GPC at 0°C which was slightly lower than that at -10°C could not be attributed to bacterial action.