Study On Quality Influence And Characteristic Metabolites Of Tomato Sour Soup Fermented By Lactobacillus Casei H1

Tomato sour soup is a condiment made by fermenting tomato as the main raw material in Guizhou Miao,Dong and other ethnic minorities areas.Tomato sour soup is popular with consumers because it is delicious and has a long history.While the traditional fermented sour soup process has the problems of complex microbial sources,easily contaminated,long fermentation cycle and unstable quality,which is not suitable for industrial development needs.In this research,the dominant lactic acid bacteria(Lactobacillus casei H1)isolated from traditional tomato sour soup was used to inoculate tomatoes for production process optimization,and the physicochemical and nutritional indicators of tomato sour soup were dynamically monitored;UHPLCQTOF-MS metabolomics method was used to study the characteristic metabolic and related metabolic pathways of Lactobacillus casei H1 fermented tomato sour soup,to clarify the effect of the Lactobacillus casei H1 of fermented tomato sour soup on its quality and function.The main results and conclusions are as follows:(1)Lactobacillus casei H1 was used to inoculate and ferment at a certain ratio.Based on the single factor test,the response surface analysis method was used to investigate the fermentation temperature,fermentation time,inoculation amount,and salt content on the quality of tomato sour soup.Optimized by Design Expert 8.0.6 software,the total acid and sensory scores were used as the double response values,the optimal production process of tomato sour soup was determined as fermentation temperature: 25?,fermentation time: 5d,and inoculation amount: 2%,salt content: 1.45%,under this condition,three parallel verification experiments were performed,and the average value of total acid was 1.23 ± 0.05%,and the sensory score was 8.48 ± 0.58.There is no significant difference from the theoretical value(P> 0.05),which indicates that the experimental value of response surface and the predicted value of regression equation basically match.The fermentation conditions of tomato sour soup are stable and reliable,determined by the model established of response surface method.(2)The physicochemical and nutritional indicators of the tomato sour soup fermented by optimizing the best production process were dynamically monitored.The results showed that: the acid production rate of H1 group was faster than spontaneous fermentation group.In the H1 group,the acidity of the 5th day(1.2 ± 0.013%)reached the acidity of the 15 th day of the spontaneous fermentation group(1.0 ± 0.013%).The total content of free amino acids in the H1 group was lower than the spontaneous fermentation group,but the content of essential amino acids in the H1 group was significantly increased by 0.0036% compared with the spontaneous fermentation group(P <0.05).The content of nitrite(0.010 ± 0.001 mg / kg)in H1 group was significantly lower than spontaneous fermentation group(0.017 ± 0.001 mg / kg)(P <0.05),which enhanced the safety of tomato sour soup.The analysis of flavor components revealed that the main volatile flavor substances in the tomato sour soup of the H1 group and the spontaneous fermentation group were alcohols,esters,and olefins.Among them,the content of esters in the H1 group was 3 times of the spontaneous fermentation group.(3)The metabolomic analysis of UHPLC-QTOF-MS was used to analyze the quality of lactic acid bacteria H1 fermented tomato sour soup and screen the differential characteristic metabolites.The results showed that inoculation of Lactobacillus casei H1 in tomato sour soup,the content of natural antibacterial substances(DL-3-phenyllactic acid and hydroxyisohexanoic acid),essential polyunsaturated fatty acids(linoleic acid and all cis-(6,9,12)-linolenic acid)and umami amino acids(L-arginine)were higher than the spontaneous fermentation group,these substances contribute to the nutritional and sensory quality of the final fermentation product.At the same time,the content of bitter amino acids(L-phenylalanine,L-leucine)during the fermentation of tomato sour soup was reduced.By integrating the metabolic pathway maps related to the characteristic metabolites of tomato sour soup,the main metabolic pathways were phenylalanine metabolism,leucine and isoleucine metabolism,TCA cycle,fatty acid metabolism,and arginine metabolism,nucleotide metabolism,fructose and mannose metabolism,pentose phosphate pathway,biotin metabolism,pantothenic acid and Co A biosynthesis.Conclusion: The Lactobacillus casei H1 used in this research can adapt well to the tomato fermentation environment and quickly produce acid,shorten the fermentation period,and improve the flavor of the tomato sour soup.At the same time,this study obtained the characteristic metabolites of Lactobacillus casei H1 fermented tomato sour soup were: DL-3-phenyllactic acid,hydroxyisocaproic acid,linoleic acid,all cis-(6,9,12)-linolenic acid and L-arginine,these metabolites serve as healthy functional ingredients in tomato sour soup,improve its nutritional health value and safety.