Lactic Acid Bacteria Community Struction Of Traditional High-salt Fermented Fish(Suan Yu) And Enhanced Fermentation

The traditional high-salt fermented Suan yu is national fermented fish products with a long history and unique flavor in Guizhou,Hunan and Sichuan.At present,the Suan yu continues to be naturally fermented by traditional family-style workshops,and has problems such as long fermentation period,contamination by bacteria,season and environment,and product instability.In this paper,the traditional high-salt fermented Suan yu in 6 different regions of Guizhou was studied,and the microbial and physicochemical properties of the product were studied.The structure of the lactic acid bacteria and the dominant strains were analyzed,and the excellent strains suitable for inoculation were screened.Add to fish for artificial inoculation fermentation.This study is of great significance for excavating the valuable high-quality lactic acid bacteria resources in Guizhou Province,promoting the industrialization of fermented fish products in China,promoting the national food economy,and improving the processing technology of freshwater fish.The results are as follows:1.The contents of lactic acid bacteria and yeast in the six groups of Suan yu were 7.14~7.65 log CFU/g and 6.21~6.54 log CFU/g.Respectively,and the enterobacter content was lower than the detection limit.The pH value is 4.14~4.77,the protein reaches 19.37~28.38%,the salt content is significantly reduced,and the water activity is 0.79~0.85.SDS-polypropylene gel electrophoresis showed that the myofibrillar protein of fish was significantly degraded.The TCA-soluble peptide was 901~1061 mg/tyrosine kg,and the free amino acid and free fatty acid were abundant.The thiobarbituric acid(TBARS)was 1.97~4.26 mg/kg,and the total amount of biogenic amine(BA)was 26-34 mg/kg,which was far below the standard limit.2.Using Illumina-HiSeq sequencing technology to explore the structure of traditional highhydrochloric acid lactic acid bacteria in different regions,it was found that Lactobacillus,Tetragenococcus and Weissella are dominant genus.Among them,the average abundance of Lactobacillus is the highest(53.99%).However,the highest relative abundance of the Suan yu B1 with the highest salt content is Tetragenococcus.3.42 strains of excellent lactic acid bacteria were isolated from 6 groups of Suan yu by the highest dilution factor method.42 strains were identified as 5 strains of Lactobacillus plantarum,Lactobacillus brevis,Lactobacillus brevis,Lactobacillus brevis,Lactobacillus acidipiscis.The Lactobacillus plantarum accounted for 57.14%.According to the analysis of strain characteristics such as acid production rate,bacteriostasis and amino acid decarboxylase activity,6 strains with rapid acid production,acid and salt tolerance,strong bacteriostatic effect,and no amino acid decarboxylase activity were screened out.The excellent strain of the potential value of the Suan yu starter was finally inoculated by the simulated system to obtain the Lactobacillus plantarum B7 with the fastest acid production rate.4.Artificially inoculated fermented Suan yu by Lactobacillus plantarum B7 and used natural fermented Suan yu as control group to detect the dynamic changes of microbial,physical and chemical and safety indicators in the fermentation process of Suan yu.Compared with Suan yu without starter,the lactic acid bacteria in Suan yu with starter grew rapidly and increased to 8.83 log CFU/g on the third day of fermentation,and the acid production rate was faster;the water holding capacity of fish muscle was rapidly reduced,and the water activity was deseased to 0.892 on the 7th day of fermentation.Lactobacillus plantarum B7 promoted protein degradation,nonprotein nitrogen(NPN),essential free amino acids and unsaturated fatty acids increased significantly;Enterobacter was below the detection limit on the 7th day of fermentation.TBARS was 0.9 mg/kg,TVB-N was 20.89 mg/100 g,the total amount of BA was 17.45 mg/kg,which was significantly lower than the inoculation group and the safety was higher.Therefore,the excellent strain B7 screened from the traditional high-salt fermented Suan yu can effectively improve the color,safety and nutrition of the acid fish product,and provide an important theoretical basis for realizing the industrial production of the traditional ethnic food.