Correlation Between Microbiota And Quality In Fermented Fish Sauce And Control Of Biogenic Amines

Fish sauce is a popular seasoning that is rich in nutrients and has a unique flavor.The quality of fish sauce is closely related to the microbial community.At present,there is a lack of systematic research on the dynamic changes of bacterial communities and the correlation between bacterial communities and metabolites during the fermentation process of fish sauce both domestically and internationally.By studying the dynamic changes,physicochemical properties,and microbial community correlation of microorganisms in fish sauce,it is helpful to control the quality of fish sauce and provide data reference for better ensuring the safe production of fish sauce.In this study,Antarctic krill,cymbidium and sardine were used as raw materials to ferment fish sauce;The succession of microbial community in the process of fish sauce fermentation was studied by high-throughput sequencing technology,and the effect of microbial community on the quality of fish sauce was determined by correlation analysis;The key strains affecting the quality of fish sauce were isolated from the fish sauce,and a bacteriocin-producing lactobacillus was screened with the main amino-producing bacteria as the indicator bacteria.The main results are as follows:1.Physical and chemical properties of fermented fish dew with different raw materialsThe quality of fish sauce fermented with different materials was evaluated by p H value,amino acid nitrogen,total soluble nitrogen,volatile base nitrogen,histamine,free amino acid and volatile compounds.The results showed that the content of amino acid nitrogen in enzymatic Antarctic krill fish sauce(A),enzymatic bacteria added Antarctic krill fish sauce(B),enzymatic bacteria added cymbidium fish sauce(C),enzymatic bacteria added cymbidium fish sauce(D),enzymatic sardines sauce(E),and enzymatic bacteria added sardine sauce(F)was 0.91,0.88,1.00,1.00,0.74,0.77 g/100 m L,and the total soluble nitrogen content was 1.24,1.35,1.57,1.33,1.23,1.29 g/100 m L,respectively.Fish sauce A,C and D meets the standard of Class I fish sauce,while fish sauce B,E and F meet the standard of Class II fish sauce;The total amount of free amino acids was 5292.77,5235.87,6383.29,5267.68,5042.35,4789.87,6498.17,6169.24mg/100 m L,respectively.Glutamic acid,alanine,leucine and tryptophan were the main amino acids in the fermented fish sauce;A total of 67 volatile compounds were detected by GC-MS,including 24 aldehydes,8 ketones,9 alcohols,5 esters,4 acids,9 alkanes,2olefins,6 nitrogenous compounds and 5 other compounds;The results of sensory evaluation showed that fermented fish sauce had unique flavor.2.Dynamic changes of bacterial community during fish sauce fermentationThe dynamic change of bacterial community during the fermentation of Antarctic krill fish sauce by enzyme method was studied using high-throughput sequencing technology,and the correlation analysis was made with the rationalization properties.The microbial diversity in fish sauce decreased gradually with the fermentation and increased slightly at the end of fermentation;The dominant bacteria in the fish sauce fermentation process are Firmicutes,Proteobacteria,Bacteroidota,Actinobaciota and Chloroflexi.The dominant bacteria are Staphylococcus(67.5%,average relative abundance),Virgibacillus(22.3%),Vagococus(5.7%),Oceanobacillus(1.2%)and Unclassified Bacillus(1.1%).PICRUSt function prediction analysis results showed that the relative abundance of unknown prediction function was the highest,followed by genes related to general prediction function and amino acid transport and metabolism.The results of correlation analysis showed that Staphylococcus had a strong positive correlation with TVB-N and histamine content;Virgibacillus was positively correlated with AAN and TSN.Staphylococcus may be the main cause of histamine accumulation in fish sauce,while the presence of Virgibacillus may be beneficial to the formation of AAN.3.Identification of microorganisms in fish sauce,and screening and research of antagonistic histamin-producing bacteriaThe dominant bacteria affecting the quality of fish sauce were isolated and identified by plate culture method,and the key strains affecting the quality of fish sauce were determined by physical and chemical properties detection and correlation analysis;Amino-producing bacteria were used as indicator bacteria to screen antagonistic bacteria from fermented foods.Four genera and nine species of microorganisms were isolated by plate culture method.The results of protease production test showed that V.Dokdonensis has a high ability to produce protease,and the detection of the ability to produce amine shows that Staphylococcus is the main amino-producing strain in fish sauce.A strain of Lactobacillus curvatus XCX1,which has inhibitory effect on amino-producing bacteria,was screened from fermented foods by double-layer agar covering method.The biological characteristics of the bacteriostatic substance produced by the strain were studied.The results showed that the bacteriostatic substance could inhibit the main amino-producing bacteria in fish sauce,and had no inhibitory effect on the main proteaseproducing bacteria.It had broad spectrum bacteriostasis,good temperature tolerance and UV stability,and was sensitive to trypsin,pepsin,neutral protease and protease K.The bacteriostatic substance was a small molecular peptide bacteriocin with molecular weight between 6.5 and 9.5 kDa.