Study On Preservation Technology And Microflora Change Of Micro-freezing Storage Combined With Modified Atmosphere Packaging Of Pseudosciaena Crocea

Pseudosciaena crocea is one of main valued fish in China.It is a traditional edible fish with rich nutrition and delicious taste.But a series of physio-biochemical reaction and the growth of microorganism after the death of fish result in the spoilage and quality decline,which make it difficult to store.Therefore,it is necessary to develop a better way to the physical preservation of Pseudosciaena crocea.In this paper,the effect of different atmosphere packaging method on the quality of Pseudosciaena crocea cultured in Ningde under the conditions of micro-freezing storage were studied by measuring the sensory quality,microbiological index,physical and chemical indexes during the storage process,so as to provide technical support for extending the storage period and improve storage quality of Pseudosciaena crocea.Also,the changes of culturable microorganisms during the storage were measured in order to preliminarily investigate the preservation mechanism of Pseudosciaena crocea using micro-freezing combined with modified atmosphere packaging technology,and provide theoretical foundation for improving the storage and preservation technology.The results are as follows:1.Under(-3.0±0.5)? of micro-freezing temperature,the storage of Pseudosciaena crocea was carried out by using different modified atmosphere packaging(air,25%CO2/75%N2,50%CO2/50%N2,75%CO2/25%N2,75%CO2/10%O2/15%N2,100%CO2).Based on the indexes of the Pseudosciaena crocea,the storage period of the Pseudosciaena crocea under six storage conditions were 21d,28d,32d,43 d,3 2d and 43 d respectively.Contrast air packaging,the sensory deficiency score,pH value,TVB-N value,K value and the total number of bacteria were lower under the condition of modified atmosphere packaging,and with the increase of CO2 proportion,the preservation effect was better.In the modified atmosphere packaging,the addition of O2 made the TBA increase and storage period shorten,which is not conducive to storage.There was no significant difference between 75%CO2/25%N2 and 100%CO2 of Pseudosciaena crocea each index.Therefore,the modified atmosphere packaging of 75%CO2/25%N2 combined with micro-frozen is the best way of Pseudosciaena crocea storage,it can significantly extend the storage period,and ensure the good storage quality.2.The 16S rDNA sequencing technique was used to analyze the changes of culturable microorganisms in Pseudosciaena crocea under the condition of micro-freezing combined with modified atmosphere packaging.The results showed that:at the end of storage,the surface of Pseudosciaena crocea cultured microorganism species were less,mainly included Shewanella sp.(55%),Pseudomonas sp.(35%),Carnobacterium maltaromaticum and Pseudomonas fluorescens,the dominant bacteria were Shewanella sp.and Pseudomonas sp.;While dominant bacteria isolated from fish intestine at the end of storage included Shewanella baltic and Shewanella sp.,also detected a small amount of Aeromonas salmonicida.Therefore,Shewanella and Pseudomonas were the dominant spoilage bacteria in Pseudosciaena crocea.And the micro-freezing combined with modified atmosphere packaging technology can effectively inhibit the growth and reproduction of spoilage bacteria and prolong the storage period of Pseudosciaena crocea.3.Isolation and identification of Pseudosciaena crocea culturable microorganisms under freezing storage conditions.The results showed that:there were various bacteria on the surface of Pseudosciaena crocea after 43d during the freezing storage,including Shewanella sp.,Shewanella putrefaciens,Pseudomonas sp.,Pseudomonas putida,Stenotrophomonas acidaminiphila and Pseudomonas mendocina,the Shewanella sp.,Shewanella putrefaciens and Pseudomonas sp.were found to be the dominant bacteria.Fewer varieties of bacteria were isolated from the intestine,mainly were Shewanella sp.and Pseudomonas sp,which was consistent with the results of other storage methods.Compared with the micro-freezing combined with modified atmosphere packaging preservation conditions,larger diversity of the microorganisms on the surface of Pseudosciaena crocea was found under the condition of frozen storage,but there was no significant difference of the microorganisms in the intestine.