| Chinese shrimp is the main aquacultured seafood in China and the main aquatic product export. It is welcome and popular due to its taste, nutrition and high medical value. However, The shrimp is proned to decay for its rich in protein, high water content as well as active autolysis enzyme. In our study, Changes of Chinese shrimp stored under vacuum packaging at different storage temperatures and different treatment methods by chitosan and ozoned water were studied, then quality changes of Chinese shrimp treated by composite bio-preservatives were observed. At last, PCR-DGGE technology was applied to assess the main microorganisms in the Chinese shrimp during the storage with the aim to offer theoretical recommendation. The experimental results were as follow:1. The results of nutritional value evaluation of proteins in Chinese shrimp and quality changes of Chinese shrimp stored at different temperature were as follow:The results showed that, proximate composition were 21.75% protein,1.6% fat,73.34% moisture and 1.31% ash. It is a high-protein, low-fat seafood. During the storage, At the lower temperature, growth of microbilological populations was retarded, changes of pH, total volatile basic nitrogen (TVB-N), the other physical and chemical parameters were also delayed. organoleptic quality was pretty good. However, the change of TBA changed was not evident during the storage, So it might not be the suitable indicator for reflecting freshness changes of Chinese shrimp during the storage. K value could reflect freshness changes, but it needed to be combined with sensory evaluation, So it could not be used as a spoilage index factor. According to the results of total viable counts, pH value, TVB-N value, hardness, the other physical and chemical parameters as well as sensory analysis, The shelf-life of Chinese shrimp stored at 4℃,0℃,-2℃under vacuum packing were 4-6d,8-10d, and 14-16d respectively.2. Effects of ozone on preservation of Chinese shrimp:In this paper, we observed that when concentration of ozone water reach 1.25mg/L, TVC was decreased by 1.08 logCFU/g. And when the concentration of ozone water between 0 and 1 mg/L, it had a significant decreasing trend of TVC, While between 1 and 1.25mg/L, the results were not evident. So it suggested that 1.0 mg/L O3 had a good bactericidal effect and was economical.Then, we used 0.5 mg/L and 1.0 mg/L O3 to deal with Chinese shrimp, quality changes of Chinese shrimp stored at 0℃were observed. At the beginning of storage, ozone water had a good effect on decreasing TVC, and the changes of hardness, total volatile basic nitrogen (TVB-N), the other physical and chemical parameters were delayed. And the effects were significant when the O3 concentration was higher. While ozone was easy to be decomposed, It could not inhibit the reproduction of bacteria and decomposition of protein at late stage. So the physical and chemical parameters in treatment group increased fast, and had no significant difference with the control group at the end of storage. So, It could not extend the shelf-life of Chinese shrimp. But it was a good pre-treatment method.3. Effects of chitosan on preservation of Chinese shrimp:Effects of different Chitosan (dissolved in 1% phytic acid solution) on Chinese shrimp were studied. The results showed that changes of pH, total volatile basic nitrogen (TVB-N), the other physical and chemical parameters were delayed, the growth of microbilological populations in Chinese shrimp treated by chitosan were retarded. The treatment group maintained a good organoleptic quality. And the effect was significant when the chitosan concentration was higher. But the changes of Chinese shrimp treated by 2.5% chitosan-phytic acid solution during the cold storage was equivalent to those groups with 1.5% concentration, it maybe due to that too high chitosan concentration reduce the effect on preservation. The best concentration of chitosan was 2%, The shelf-life could be extended to four days when compared to the control group.4. Effects of complex preservation on preservation of Chinese shrimp:First of all, Chinese shrimp was treated by lmg/L ozone to reduce initial TVC, coated by chitosan-phytic acid solution, vacuum packaged, and stored during partial storage (-2℃), To the control group, Chinese shrimp were immersed in distilled water, vacuum packaged after drained. The results showed that initial TVC of Chinese shrimp treated by ozone and chitosan were 3.81 log CFU/g, far lower than the control group (5.04 log CFU/g). During the storage, the composite preservation inhibited the changes of pH, total volatile basic nitrogen (TVB-N), the other physical and chemical parameters, retarded the growth of microbilological populations, reduced the redness value, and maintained good organoleptic quality. According to the results of TVC, pH, TVB-N, hardness, the other physical and chemical parameters as well as sensory evaluation, the shelf-life of Chinese shrimp treated by composite preservation was extended to 10d when compared with the control group.5. Molecular microbiology research of Chinese shrimp treated by composite preservative technology in the dynamic monitoring: In this paper, PCR-DGGE technology was applied in Chinese shrimp treated by complex preservation. The results showed that, the effect of Touch-down PCR was better than the common PCR. During the storage, the domain bacteria of the control one in the early stage of storage were Aeromonas punctata and Aeromonas punctata, and in the middle and end of the storage, the domain bacteria were Aeromonas punctata and Aeromonas salmonicida, the domain bacteria of the treatment samples in the early stage of storage were Aeromonas hydrophila. in the middle of the storage, the domain bacteria were Aeromonas punctata and Aeromonas hydrophila. in the middle of the storage, the domain bacteria were Shewanella xiamenensis and Shewanella baltica.
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