| The effect of different killing methods on the fresh quality of turbot was researched in this article. Turbots were grouped and treated respectively as follows: (1) stimulated electrically with 220V pulsed direct current (PDC) for 1 min (M1); (2) choked the turbot to death in a box filled with CO2 (M2); (3) exsanguinated lively into bins of ice slurry for 1 h (M3); (4) killed directly by a percussive blow to the head and stored in ice(M4). After killed all fishes were stored in a thermostat container of 0℃. K-value,lactic acid and pH-value were measured in different time. The results showed that M4 was the best killing method to keep fish freshness which had a slow change of K-value, the minimal K-value in 72 h (M1 36.19%, M2 55.46%, M3 57.11%, M4 35.93%), the minimal lactic acid content (M1 1.741mg/g, M2 2.464mg/g, M3 1.991mg/g, M4 1.536mg/g) and the max pH-value (M1 6.99, M2 6.78, M3 6.91, M4 7.14) when they just died.Controlled freezing-point and modified atmophere packing can prolong the shelf life of turbot by restraining the growth and reproduction of bacteria. based on sensory evaluation and chemical indicators, controlled freezing-point and modified atmophere packing was better than other preservation methods. The results showed that the shelf life of controlled freezing-point cooperateing with 60%CO2 storage, controlled freezing-point cooperating with 30%CO2 storage, controlled freezing-point cooperating with vacuum, 4℃+60%CO2, controlled freezing-point storage, ice storage was 29d, 25d, 21d, 18d, 18d, 15d, respectively.The microbial flora changes and identification of the dominant spoilage microorganisms during controlled freezing-point storage(0--1.3℃) and 60%CO2 storage on farmed turbot were studied. Controlled freezing-point storage: 568 strains were isolated and identified from skin at day 1, 7, 12, and 23 during storage. A stepwise procedure using simple phenotypic tests was used to identify the isolates and proved a fast way to deal with a large collection of microorganisms. Microflora in fresh farmed turbot was consisted of 43.3% Gram-negative bacteria (Flavorbacterium-cytophaga group 19.5%), and 53% Gram-positive bacteria (Micrococcus spp. 20.7%). The microflora of spoiled sample was consisted of 92.2% Gram-negative bacteria and 7.8% Gram-positive bacteria (Micrococcus spp.). After 23days, the highest change in microflora was observed in the Flavobacterium-cytophaga group (19.5% to 43.7%)and Shewanella (1.8% to 33.3%) .A significant presence was also noted for Micrococcus spp.(20.7% to 6.3%). Overall the dominant organisms were Shewanella spp. and Flavorbacterium-cytophaga group. Controlled freezing-point cooperating with 60%CO2 storage: results showed that G-can live better than G + in high concentrations of carbon dioxide and anaerobic. There were few lactic acid bacteria in initial microbial flora, Lactococcus 0.6% only. Lactic acid bacteria were increasing during storage, Heterofermentative, Lactobacillus, Lactococcus and Streptococcus increased to 16.7%,24%,7.4%,3.7% respectively on day7. The Lactococcus and Streptococcus were increasing to 33.3% and 8.3%, however Heterofermentative, Lactobacillus decreased to 8.3%,13.9% respectively on day18. When the turbot spoiled(day30), the Lactococcus and Streptococcus were reach to 50% and 16% respectively and the total of Flavobacterium-cytophaga group and Shewanella (SSO of controlled freezing-point storage) decreased to 9%. So Lactococcus and Streptococcus were considered as the SSO during controlled freezing-point cooperating with 60%CO2 storage. It is indicated that the species and amount of SSO could be changed from cold storage during controlled freezing-point cooperating with 60%CO2 storage.
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