Application of supercooling to long-term storage of fish meat

Fish meat was brought to a supercooled state through slow cooling, and changes in the texture, histology, and protein composition of the meat were investigated. The groups whose storage temperature were lowered by 1.0°C per day (the 1.0°C group) and 0.5°C per day (the 0.5°C group) began to freeze in the vicinity of −3.5 and −5.0°C, respectively. The freezing point depended on the fish species; the lowest freezing point was −8.5°C, for the red sea bream in the 1.0°C group. The breaking strength tended to decrease more slowly in the 1.0°C group, but the collagen fibers collapsed more rapidly in the 1.0°C group. In SDS electrophoresis, a slight change in the banding patterns was observed, but the relationship between this observation and changes in histology and physical properties was unclear. This study shows that it is possible to produce a supercooled state in fish meat, and demonstrates that supercooling is a potential new storage method that lowers the temperature without generating ice crystals.     

Attachment of Vibrio parahaemolyticus strains to estuarine algae.

Attachment of Vibrio parahaemolyticus strains to estuarine microalgae was examined in artificial seawater by viable counts of the organism and direct counts of the bacterial cells after immunoperoxidase staining. Thermostable direct hemolysin (TDH)-producing and TDH-non-producing strains of V. parahaemolyticus were found to attach to five estuarine strains of Navicula (diatom alga) in similar levels. The level of the bacterial attachment depended on salinity and temperature of the water, in which the maximum attachment was observed in 15% artificial seawater at 25 degrees C, a typical condition of Hashizu estuary in Japan during summer months. The attachment was inhibited by pectinase digestion of the algal cells. These evidences confirmed the participation of the microalgae to the ecological cycle of V. parahaemolyticus at the estuary.