Effect of freezing conditions on the extractive component in oyster Crassostrea gigas.

We investigated the effect of freezing conditions on the extractive components in the frozen raw oysters. Oyster with shell or shucked oyster was frozen individually in liquid nitrogen or ethanol brine below -40°C within 3 min for shucked oyster and 23 min for oyster with shell. Also oyster was frozen at -20, -10 and -5°C in a freezer. Free amino acids, organic acids, and nucleotides in the extracts from these frozen oysters were analysed. The total OA contents in the frozen shucked oysters was significantly higher than that in the raw oysters except frozen with ethanol brine. There was no significant difference in total FAA contents in the shucked oysters among different freezing conditions. But the total FAA contents tendency increased by freezing except ethanol brine freezing. These facts suggest that freezing with ethanol brine is effective for freezing of shucked oysters. On the other hand, contents of free amino acids and organic acids in oysters with shell frozen at -5 and -10°C were significantly lower than the shucked oysters frozen at same conditions.