Effect Of Lactic Acid Bacteria On Proteolysis Of Fermented Sausages

In order to study the effect of lactic acid bacteria on protein decomposition of fermented sausages,this paper will select lactic acid bacteria with high protease production,study of its effect on proteolysis and microbial flora of fermented sausages,predict the metabolic pathways associated with protein decomposition by microbial flora,and analyze the correlation between microbial flora and protein decomposition.The experimental results were as follows:Among the 12 test strains,Lactobacillus plantarum CM48 and CM27 could tolerate the growth environment of 6%Na Cl,p H4.5,150mg/kg of Na NO₂,and the fermentation did not produce physical amines,among which Lactobacillus plantarum CM48 was strong in the catabolism of sarcoplasmic proteins and Lactobacillus plantarum CM27was strong in the catabolism of myogenic fibrous proteins,and the protease producing activity was 25.00U/m L and 25.09U/m L,which were significantly higher than the other strains（P<0.05）.The results of applying Lactobacillus plantarum CM27 and CM48 as fermenters to fermented sausages for the determination of relevant indexes showed that during the fermentation process,the p H and Aw decrease rate of CM48 and CM27 groups were significantly higher than that of ZR group,a*was higher than that of ZR group,and TVBN content was significantly lower than that of ZR group（P<0.05）.The analysis of proteolytic properties of fermented sausages showed that the proteolytic index,aminopeptide nitrogen and TCA-soluble peptide of fermented sausages showed an increasing trend with the prolongation of processing time,in which the increase rate of CM48 and CM27 groups was significantly higher than that of ZR group（P<0.05）.And as shown by the SDS-PAGE gel electrophoresis plots,for sarcoplasmic proteins,the 100-75k Da bands in CM48 group disappeared completely at 30d,and the 100-75k Da bands in CM27 group disappeared completely at 60d,while the intensity of the bands in ZR group was weakened.actin,pro-myosin,troponin and myosin light chain bands in CM48 and CM27 groups of fermented sausages The intensity of staining was lower than that of the ZR group.By analyzing the volatile flavor compounds,the aldehydes and terpenes in the CM48 group were higher than those in the ZR group,while the alcohols and lipids in the CM27 group were higher than those in the ZR group.And the relative contents of1-octen-3-ol,ethyl octanoate,ethyl decanoate,ethyl caproate,ethyl heptanoate,heptanal,and nonanal were higher in the CM48 and CM27 groups.Among them,1-octen-3-ol and trans-2-nonenal were the key flavor compounds unique to CM48 and CM27 during storage,which imparted mushroom flavor and fat-like aroma to the fermented sausages.Microbial flora diversity analysis of fermented sausages showed that with the increase of processing and storage time,the CM48 group had lower diversity and species richness of its fermented sausage sausage community compared with the ZR group,and the highest percentage of thick-walled phylum dominant in each group,of which the abundance of thick-walled phylum in the CM48 group increased from 99.78%to 99.90%,of which Lactobacillus were all dominant.A total of 20 functional metabolic pathways were annotated at the KEGG level in the sausage,among which the metabolic pathways related to proteolysis were amino acid biosynthesis,phosphate transporter system,pyruvate metabolism,cysteine and methionine metabolism,and the expression of related metabolic pathways increased with the extension of processing time.The correlation analysis of microbial flora and proteolytic-related indicators showed that Lactobacillus were positively correlated with AAN and TCA-soluble peptide（P<0.01）,and unclassified Lactobacillus were significantly positively correlated with PI（P<0.001）.The correlation analysis between microbial flora and proteolytic-related indicators showed that Lactobacillus were mainly positively correlated with esters.