Correlation Between Dominant Bacterial Community And Non-Volatile Organic Compounds During The Fermentation Of Shrimp Sauces In Cangzhou,Hebei Province

Shrimp sauce is a kind of fermented food obtained by mixing raw materials with a certain proportion of salt(15%-30%)and then fermenting.It is widely used as a culinary condiment due to its unique flavor and rich nutritional value.Shrimp sauce is generally fermented naturally since sterilization is seldom performed during production.Differences in the natural climatic conditions and microbial activities combined with ingredient types may be responsible for their diversity of nutritional,organoleptic and quality in the final fermentation product.The traditional shrimp sauce natural fermentation process has the disadvantages of large temperature fluctuation,long time consumption and high salt content.These shortcomings are not conducive to the industrialized production of shrimp sauce and the standardization of quality and are not in line with the current low-salt diet.In this paper,this study was to establish the correlation between bacterial diversity and non-volatile organic compounds.In this study,the core microorganisms in the fermentation process were identified,and the core microorganisms were screened,and their growth characteristics were studied.The screened strains were used as starter for fermentation,and the effect of starter on physicochemical properties and non-volatile organic compounds during the fermentation of shrimp sauce was analyzed.It will provide a foundation for the establishment of new technology for product quality control.The results obtained are as follows:1.Correlation analysis between non-volatile organic compounds and bacterial community changesThis study used high-throughput sequencing technology to study the bacterial community changes during shrimp sauce fermentation.Bacteroidetes,Actinobacteria and Proteobacteria were dominant in the early stage of fermentation.But the bacterial community was more stable in the later stage of fermentation.Firmicutes and Tetragenococcus were the dominant bacterial phylum and the dominant bacterial genera,respectively.Spearman analysis was used to analyze the correlation between nonvolatile organic compounds and bacterial community changes.It was found that there was a certain degree of correlation between most bacterial genera and taste active substances during the natural fermentation of shrimp sauce.Tetragenococcus was positively correlated with various free amino acids,and Staphylococcus was positively correlated with taste nucleotides.Therefore,Tetragenococcus and Staphylococcus are the core genera that affect the non-volatile components in the shrimp sauce fermentation process,which provides a theoretical basis for improving the shrimp sauce fermentation process.2.Screening of fermented strains in shrimp sauce8 strains were isolated and purified from naturally fermented shrimp sauce using traditional culture methods.5 strains were identified as Staphylococcus epidermidis(R1-2,R1-3,R1-4,R1-5,R1-7).2 strains were Tetragenococcus halophilus(R4-7,R4-9).1 strain was identified as Tetragenococcus muriaticus(R5-11).The 5 strains of Staphylococcus screened have strong acid-producing ability and grow better under the culture conditions of salt concentration of 0%-10%,culture temperature of 25-35 ℃,p H 6.0-p H 8.0;3 strains of Tetraphylococcus grow well under the conditions of salt concentration of 5%-15%,culture temperature of 25-35 ℃,and p H 6.0-p H 9.0.The screened strains provided a basis for subsequent use as the starting starter for shrimp sauce fermentation.3.Tetragenococcus and Staphylococcus as potential starters to improve quality of shrimp sauceA potential starter was created by using Tetragenococcus(T)and Staphylococcus(S)with a strain ratio of 1:1.The conditions for rapidly fermented shrimp sauce: salt addition is 8%(W/W);mixed starter culture inoculation amount is 2%(V/W,bacterial concentration: 7 log CFU/m L);fermentation temperature is 20 °C.The formation of non-volatile taste substances during the fermentation process was analyzed.The addition of starter culture can inhibit the production of TVB-N and increase the content of AAN;the addition of starter culture can enrich the types and content of FAA,and the content of organic acids and nucleotides.Among them,the T+S group(Tetragenococcus and Staphylococcus)had the highest nucleotide content,which could make the umami in the shrimp sauce more obvious.Through electronic nose analysis and sensory evaluation,it was found that the addition of mixed starter culture could produce good flavor.Therefore,the addition of mixed starter culture can improve the fermentation rate and control the quality of shrimp sauce.