Effect of super-chilling storage on maintenance of quality and freshness of the Pacific oyster(Crassostrea gigas)

The quality changes of shelled Pacific oysters(Crassostrea gigas)were examined in relation to the effects of superchilling storage at-1 C for 28 d by measuring changes in biochemical properties(microbial analysis,adenosine triphosphate(ATP)-related compounds,pH,free amino acids)and sensory evaluations in this study.The results indicated that microorganism growth was significantly inhibited during superchilling storage.Adenosine diphosphate(ADP)and adenosine monophosphate(AMP)accumulated while ATP rapidly decreased in the adductor muscle.ATP and ADP were the primary components in the other 3 tissues including mantle,gill,and body trunk of oysters,and they remained relatively stable over time.The pH and adenylate energy charge in the adductor muscle could be utilized as freshness indicators for shelled oysters.However,there were no significant differences(P>0.05)among the free amino acids during whole storage.According to the sensory evalu-ations,oysters could be alive and tolerated up to 21 d at-1℃storage.The study demonstrated that superchilling storage at-1℃could better maintain the eating quality of shelled oysters and the shelf life was extended to 21 d.

Effects of flash-boil shucking on biochemical,sensorial and ultrastructural properties of Yesso Scallop(Mizuhopecten yessoensis)adductor muscle during refrigeration

Scallop adductor muscle has great popularity for raw consumption in Japan,but conventionally shucking live scallops with high vitality by knife requires skill and is time-consuming.Flash-boil shucking is a convenient shucking method in sushi restaurants for live scallops.However,the effects of this treatment on the quality of its main edible part,the adductor muscle,are not clear.This study was conducted to investigate the impact of flash-boil shucking on the quality of raw-edible scallop adductor muscle,focusing on flavor-enhancing components and ultrastructure.Thermal treatment could contribute to the formation of flavor-enhancing nucleotides in the external layer of the adductor muscle.Adenosine monophosphate content increased with the boiling time,which significantly increased to 1.47±0.42μmol/g in the 30 s-boiled group compared with 0.38±0.13μmol/g in the control group(p<0.05).The rapid adenosine monophosphate accumulation after boiling resulted in a faster accumulation of inosine and hypoxanthine during subsequent refrigeration,which could bring bitterness to aquatic products.Flash-boil shucking had no discernible effect on the proportion of free amino acids relevant to the flavor of scallop adductor muscle,despite the possibility of a reduction in total free amino acids.The external layer of the scallop adductor muscle could be hardened after flash-boil shucking.At the ultrastructural level,muscle fibers tend to aggregate transversely and contract longitudinally depending on the heating time.Flash-boil shucking is ideal for consuming the raw-edible scallop adductor muscle promptly.Flash-boil shucking treatment is recommended for households,restaurants,and small factories for treating scallops with high vitality.