Effect of Cold Dormancy Combined with Film Packaging on Quality and Metabolism of Crassostrea gigas during Ecological Ice Temperature Keep Alive

To optimize the oyster circulation operation mode and investigate the effects of different pre-treatment methods on the vitality and quality of oysters during the anhydrous preservation period, the actual industrial transportation was simulated, the harvested Crassostrea gigas were transported by cold chain to the place of sale, after artificial seawater recovery and depuration, they were treated in bulk and low temperature induced dormancy with film wrapping respectively and then treated under ecological ice temperature (0 ℃) for waterless preservation. The survival rate, weight loss rate, total bacterial count and coliform and muscle quality of oyster were measured. The results showed that the survival rate of oysters in the cold dormant film group was still higher than 95% when they were kept in ecological ice temperature without water for 9 d. The weight loss rate was 3.95%, which was significantly better than that of the bulk treatment group (P<0.05); the total bacterial count and coliform in all groups of oysters met the international limits after 9 d. The inhibition of the growth and reproduction of microorganisms of oysters treated by cold dormancy combined with film wrapping was more obvious (P<0.05); with the extension of the preservation time, the rate of deterioration of L^* and ∆E values of oysters in bulk treatment group was significantly faster than that of the cold dormant film group (P<0.05); the rate of decline in adductor muscle hardness, elasticity, adhesion and chewiness was also more pronounced in the bulk treatment group. After 9 d of preservation, the TVB-N content of oysters in the bulk treatment group increased by 2.4 times; TBA values increased slightly in the cold dormant film group and the quality of muscle was significantly better than that of the bulk treatment group (P<0.05) while the microstructure also showed a better compactness of oyster muscle in the cold dormant film group. The study shows that compared with the bulk treatment after purification, the cold dormancy with film wrapping pre-treatment can effectively improve the survival rate of live oysters in circulation and slow down the rate of muscle quality deterioration, this preservation pre-treatment mode is significantly better than the live Crassostrea gigas circulation mode commonly adopted by domestic e-commerce nowadays.