| Longxi bacon is a kind of traditional fermented meat products.However,the effect of microbial community succession on the formation of flavor is still unclear.In this study,based on the traditional Longxi bacon production technology,high-throughput sequencing technology was used to study Longxi bacon microbial diversity and community succession in the process of production;meanwhile,gas chromatography-mass spectrometry was used to detect volatile flavor compounds and the change of free fatty acids,as well as other physical and chemical indexes.On the basis of these results,the relationship between the microbial community succession and the change of flavor components of traditional Longxi bacon was explored.This study aims to provide a theoretical basis for revealing the flavor formation mechanism of traditional longxi bacon.The main results obtained in this study were as follows:1.Based on high-throughput sequencing analysis,the composition of dominant flora in longxi bacon was determined.At the genus level,the dominant bacteria were Brochothrix,Carnobacterium,Lactobacillus,Pseudoalteromonas,Psychrobacter,Cupriavidus.And the dominant fungi were Trichoderma,Phoma,Guehomyces,Cryptococcus,Bullera.In addition,the community composition and diversity of microbiome were in a dynamic change with the processing process(curing and drying).2.The microenvironmental conditions(sodium chloride content,pH,Aw,total sugar)and their variation rules of Longxi bacon substrate were clarified.The results showed that the contents of sodium chloride and total sugar gradually increased,while the Aw gradually decreased,and the pH changes generally tended to be stable,ranging from 6.0 to 6.5 in each period except for the sample in the middle stage of curing(5.8).In addition,the acid value and peroxide value gradually increased during the production process.The total protein content and amino acid nitrogen gradually increased with the preparation,and the proteolysis degree gradually decreased.3.The changes of volatile substances and free fatty acids were detected by gas-mass spectrometry.The results showed that 84 volatile components including hydrocarbon,aldehyde,ester,alcohol,organic acid and ketone were detected and identified.The main free fatty acids were palmitic acid,stearic acid,palmitic acid,oleic acid and linoleic acid,accounting for 83.84%~92.43%.The results of ROAV analysis showed that aldehydes,ketones and esters contributed the most to flavor.The results of principal component analysis of key flavor substances showed that ethyl caproate,anisole,hexaldehyde,3-methyl-butyraldehyde,2-octenaldehyde and linalool could distinguish the samples of different stages well.4.Pearson correlation analysis was used to analyze the relationship between microorganisms and key flavor substances and major fatty acids.The results showed that the microorganisms related to S12(2-octene aldehyde)were mainly Cupriavidus,Oxalobacteraceae,Acinetobacter,Lactococcus,Sphingomonas,Trichoderma,Acremonium.The microorganisms related to S13(3-methylbutyraldehyde)were mainly Lactobacillus and Aspergillus.The microorganisms related to S19(Ethyl caproate)were mainly Lactobacillus,Macrococcus and Yarrowia.Staphylococcus,Micrococcus,Aspergillus were mainly related to S16(hexaldehyde).The microorganisms related to S20(ethyl octylate)were mainly Streptococcus,Erysiphe,and Pseudogymnoascus,and the microorganisms related to S28(linalool)were Trichoderma,Acremonium,Cupriavidus,Oxalobacteraceae,Staphylococcus,Acinetobacter,Sphingomonas,Lactococcus,Thermus.The results of correlation analysis between microorganisms and fatty acids showed that Streptococcus,Lactobacillus and Bullera were significantly correlated with saturated fatty acids and polyunsaturated fatty acids.Carnobacterium,Staphylococcus,Brochothrix,Cupriavidus,Penicillium and Trichoderma were significantly correlated with the contents of unsaturated fatty acids,such as palmioleic acid,oleic acid and linoleic acid.5.We analyzed the major microorganisms associated with flavor during preparation.The results showed that Staphylococcus,Lactobacillus,Micrococcus,Aspergillus,Yarrowia,Trichoderma,and Penicillium were significantly correlated with the key flavors,which may be the core bacteria related to flavor.In summary,by using high-throughput sequencing technology to analyze the microbial diversity and community structure,the succession rules of the microbial in the production process of longxi bacon is defined.Based on the analysis of volatile components and the mining of flavor material data(the mining of fat metabolism and protein hydrolysis)to clarify the flavor change rules of Longxi bacon in the production process.It provides a theoretical basis for revealing the flavor formation mechanism of traditional longxi bacon. |
