Isolation And Identification Of Lactobacillus And Controlled Fermentation Technology Researching Of Sour Fish

As a traditional fermented food in our country,sour fish plays an extraordinary role in people,s especially Xiangxi people,s daily diet.Due to manufacturing produce method,It,s more easily infected with bad microbes,dust or other pollution sources.The cycle of fermention is very long.It easily affected by season and environmental factors.And the quality of sour fish is unstable and it is hard to be standardized.At present,there are only few reports on sour fish,and more traditional analysis methods on the research of isolation and identification of lactobacillus in the natural fermented sour fish.In this paper,natural fermented sour fish was the research target,and traditional analysis methods and ERIC-PCR technology were used to research lactobacillus of natural fermented sour fish.And the lactobacillus isolated was applied to the process of the artificial inoculation fermentation.The principal results were fits follows:1.Using grass carp as experimental test specimen,the factors on natural fermentation process were researched.The optimal conditions including 7% of salt addition,15% of millet addition,20 h of soaking time and 50 d of fermentation time at rome temperature.Under these conditions,the amino nitrogen and volatile base nitrogen of sour fish were respectively 0.1502g/100 g and 52.35mg/100 g,and the sensory value of sour fish was 91.At the same time,HS-SPME and GC-MS were used to analyze volatile flavor compounds in sour fish.49 kinds of flavor components were identified,among which aldehydes and esters made a larger contribution to the flavor of sour fish.2.Using traditional analysis method and ERIC-PCR technology to isolate and identify lactobacillus in sour fish.The experiment slected 3 bacteria(S1,S2 and S3)which obtained from preliminary separatioin to DNA extraction,amplifing gene fragment and gene sequencing.The results showed that S1 and S2 have a close relation to lactobacillus,S3 has a close relation to Lactobacillus casei.Combined with classical taxonomy,physiological and biochemical characteristics and molecular characterization we can reach the conclusion that S1 and S2 were lactobacillus,S3 was Lactobacillus casei.3.Using Lactobacillus of S1 and S2(the acidogenicity of S1 and S2 was better than S3)isolated by this experiment to do the experiment of artificial inoculation fermentation.The fermentation conditions were studied by response surface methodology.The optimal conditions including 7% of salt content,5% of inoculating Lactobacillus,42 d of fermentation time.Under these conditions,the quality of sour fish is as good as the quality of natural fermentation sour fish,and the production cycle was reduced by approximately one week.