Study On Dominant Bacteria Of Refrigerated Large To Yellow Croaker And Japanese Seabass

China ranked first in the world of output of aquatic products. Consumption of the large yellow croaker and the Japanese seabass were becoming popular in China’s coastal areas, due to its delicious flavor and tender taste rich of amino acids essential for human and rich vitamins. However, because they contain abundant fatty acids, especially higer content of unsaturated fatty acid, which will produce oxidation and rancidity, etc; After fishing,the fresh is descending fastly.With the development of economy and the improvement of living standards, the better quality and safety of aquatic products are required in the the domestic and foreign market, which present a new challenge for the aquatic preservation technology. Meanwhile, the activity of endogenous enzymes and microbial reproduction causes for the quality deterioration of aquatic products during the storage, especially special spoilage bacterial. Thus, it was the basis of quality change monitoring and spoilage bacterial suppression that micro flora changes in aquatic products during and identification of specific spoilage were studied.Therefore, the aim of the present study was to evaluate the quality of yellow croaker and the Japanese seabass by the sensory, physicochemical and microbiological methods during refrigerated storage. The changes of microbial community in two kinds marine fish were analyzed by selected culture and PCR-DGGE. Furthermore, the spoilage activity of main bacteria isolated was studied, and specific spoilage organisms (SSO) were identified.The main results are as followed:1. The effects of two cold temperature on the quality of yellow croaker and Japanese seabass presented significant difference. The better freshness, lower K value and TVB-N in the marine fish at-2℃compared with4℃. The shelf life of two kinds of marine fish extend7days at-2℃than4℃. Large yellow croaker was easier to deterioration than Japanese seabass during the cold storage, which the shelf life of Japanese seabass prolonged3days and7days at4℃and2℃than large yellow croaker, respectively. It was attributed to higher protein in large yellow croaker causing the reproduction of bacteria and accumulation of biogenic amines. The total viable counts (TVC) increased gradually with time in the yellow croaker and Japanese seabass using two kinds of culture, PC A and LH. Additionally, the number of bacterial was more in LH than PCA. Similar increase between TVC and producing H2S bacteria, Pseudomonas, Photobacterium phosphoreum were observed, whereas, growth of lactic acid bacteria and Enterobacter was slowed.2. PCR-DGGE technology had been built to analyze the diversity of bacterial in large yellow croaker and Japanese seabass. The main bacteria was identified by sequencing. Results of DGGE profiles showed that the diversity of DGGE increased and bands became brighter with storage time both in two kinds of fish. Similar diversity of DGGE profiles was observed both at-2℃and4℃in the same marine fish. Furthermore, significant difference of the diversity of DGGE were found between large yellow croaker and Japanese seabass. More bands in DGGE profile were detected in the culture of LH and PC A than no-culture sample. The sequencing results indicated that main bacterial of two kinds of fish were producing H2S strains and pseudomonas, which accounted for50%and40%in large yellow croaker and40%and20%in Japanese seabass, respectively. So, similar changes of bacterial community in the culture and PCR-DGGE was observed.3. From the number of the microbial count, the SSO are producing H2S strains and Photobacterium.When a single colony inoculated to fish block,from the sensory evaluation, the Photobacterium is the colour and lustre of influence on the quality of fish block. And producing H2S strains is advantage corruption bacterium to the large yellow croaker and the Japanese seabass in low temperature storage. From the sensory scores, screening the strongest corruption ability ofproducing H2S strains were XH6(the large yellow croaker) and XL4(Japanese seabass). Analysising the ability of corruption by microbial count result, at0day, the total bacterial of the large yellow croaker was more than the Japanese seabass because of the much stronger microbial adhesive. Therefore, the shelf life of the large yellow croaker was shorter.4. Based on Gram stain, XH6and XL4were both Gram-positive bacillus. The identification results of physiological and biochemical and16SrDNA sequence were same,XH6and XL4were Shewanella putrefaciens.