Study On The Improvement Of Fish-chili Paste Quality By Inoculating Starter Cultures

Traditional fish-chili paste is a kind of fermented seasoning food with typical ethnic characteristics in southwest China.However,the time for spontaneous fermentation is long and it is difficult to guarantee the safety.The inoculation of artificially selected strains for fermentation can effectively improve product quality and accelerate the process,and this method has been widely used in the production of fermented food.This study is dedicated to evaluating the quality characteristics of commercial products,and starter cultures with higher esterase and acid production ability were selected,and applied to study their effects on the quality and safety of fermented fish-chili paste using low-value freshwater silver carp and chili as the main raw materials.It is of great significance for in-depth understanding of the quality formation process of fish-chili paste and the directional quality control.Firstly,the quality and safety characteristics of five commercial fish-chili pastes were studied.The odor activity value(OAV),relative odor contribution(ROC)and statistical methods were used to analyze the key volatile flavor substances in the commercial fish-chili pastes and their correlation with sensory attributes.The results showed that the pH of the products is between 3.95 and 4.04,and lactic acid was the main organic acid.The content of umami free amino acids(aspartic acid and glutamic acid)accounted for 13.50%-15.89% of the total FAA content,and the content of polyunsaturated fatty acids(PUFA)in free fatty acids(54.37%-57.58%)is the highest.The content of nitrite is significantly lower than the limit(20 mg/kg).The total amount of biogenic amines exceeded the FDA limit of aquatic products(1000 mg/kg),and putrescine,cadaverine,histamine and tyramine were the main biogenic amines.A total of 76 volatile flavor substances were detected by SPME-GC-MS.According to the OAV and ROC,ethyl acetate,isoamyl acetate,ethyl caprate,linalool and limonene were the key volatile flavor substances.Correlation analysis between volatile flavor and sensory attributes showed that ethyl acetate,isoamyl acetate and ethyl caprate were positively correlated with the fruity and estery sensory characteristics.Secondly,4 kinds of bacterial starter cultures(SBM52,PROMIX5,WBX43 and V3)were selected using the esterase and acid production capacity as the main indicators,and the effects of the starter cultures on microbial flora changes,flavor components and safety during the fermentation of fish-chili paste were studied.The results showed that the lactic acid bacteria in the inoculated groups grew faster,and they could quickly produce acid and obtain lower pH value.The activities of neutral and acidic proteases continued to increase as the fermentation progressed,and the protein continued to degrade.Compared with the spontaneous fermentation group,more umami and sweet free amino acids accumulated in the inoculated groups,and the ratio of unsaturated fatty acids and saturated fatty acids had increased to varying degrees.After 8 weeks of fermentation,the total content of key esters volatile substances in the SBM52,PROMIX5,WBX43 and V3 groups increased by 36.38%,1.77%,54.78%,and 27.94%,respectively,compared with the control group.The content of biogenic amines in SBM52,PROMIX5,WBX43 and V3 groups decreased by 64.64%,88.81%,66.58% and 93.87%,respectively.Microbial flora analysis results showed that the bacterial diversity in all groups was higher than that of fungi,and the microbial diversity in the inoculation groups was more abundant than that of the control group.Lactobacillus and Weissella were the dominant bacterial genus in all groups.Among them,SBM52 and WBX43 also contained Pediococcus and Staphylococcus,respectively.The dominant fungal genus in the inoculated groups was Pichia.Finally,the effects of combination fermentation of aroma-producing yeast(H)and SBM52(HS),WBX43(HW)and V3(HV)starter cultures on the quality and safety of fish-chili paste were studied.Microbial analysis showed that yeast and lactic acid bacteria could rapidly proliferate,and Enterobacteriaceae was rapidly inhibited.After 8 weeks of fermentation,the total content of biogenic amines in H,HS,HW and HV groups decreased by 62.84%,70.18%,73.83% and 79.48% compared with the control group,and HS and HW further decreased by 12.02% and 18.32% compared with the SBM52 and WBX43 groups,respectively.The proportion of umami amino acids in the inoculated groups(19.16%-26.21%)was significantly higher than that of the control group(17.13%).The content of key ester volatile flavor substances in the H,HS,HW and HV groups was1.28,1.89,3.00 and 1.66 times that of the control group,respectively,and the ethyl acetate content in the HS,HW and HV groups further increased by 75.31%,145.65% and 63.96% compared with that of SBM52,WBX43 and V3 groups.These results showed that the combined application of aroma-producing yeast and bacterial starter cultures could further significantly increase the ester volatile flavor substances on the basis of effectively inhibiting the biogenic amines production.