Study On The Application Of Lactiplantibacillus Plantarum LP-6 In Fermented Soymilk

Fermented soymilk is a healthy fermented beverage similar to yoghurt made by fermenting single or compound lactic acid bacteria,which has the effect of lowering blood pressure and improving intestinal health.However,the poor stability of fermented soymilk,the strong smell of beans and the serious acidification during storage have led to the unacceptability of fermented soymilk to the general consumers.Therefore,in this thesis,Lactiplantibacillus plantarum LP-6,isolated from a traditional fermented koumiss sample from Tianshan Farm,Wusu,Yili Prefecture,Xinjiang,was fermented with a single strain of Streptococcus thermophilus S10,which has good fermentation characteristics in soymilk,as well as a combination of the two strains in soymilk.The fermentation characteristics,storage stability,soybean isoflavone content,volatile flavour substances and sensory evaluation of the fermented soymilk were analysed to investigate the effect of Lactiplantibacillus plantarum LP-6 on the fermentation characteristics and storage stability of the fermented soymilk,and to provide theoretical basis and data to support its commercial application.The specific results are as follows.(1)The fermentation times of the Streptococcus thermophilus S10 single-strain fermentation group,the S10+LP-6 compound fermentation group and the Lactiplantibacillus plantarum LP-6 single-strain fermentation group were 12.08 h,11.35 h and 19.61 h,respectively.(2)During storage,the p H value of each group decreased significantly(P<0.05)and the titratable acidity increased significantly(P<0.05),and there was no significant difference between the groups(P>0.05);the viable bacteria count and viscosity of the compound fermentation group were always significantly higher than the other two groups(P<0.05),and its viable bacteria count reached 1.22×10~8 CFU/m L at the end of storage.In addition,the water-holding capacity and soy isoflavone content of the groups were not significantly different(P>0.05);the hardness,cohesiveness and consistency of the compound fermentation group were higher than those of the other two groups as shown by the physical properties.(3)In addition,the volatile flavour substances in the fermented soymilk samples of the three groups were measured at the end of fermentation.20 volatile flavour substances were detected,among which the content of substances that caused the fermented soymilk to have a beany flavour,such as hexanal and 2-pentyl furan,was significantly lower in the compound fermentation group than in the other two groups(P<0.05).In the sensory evaluation,the compound fermentation group had a uniform colour,high viscosity,moderate tissue condition,fine and lustrous surface,no bad taste and odour,and a significantly higher score than the other two groups(P<0.05).In conclusion,the fermentation of a strain of Lactiplantibacillus plantarum LP-6 with a strain of Streptococcus thermophilus S10,which has good fermentation characteristics in soymilk,resulted in a reciprocal effect between the strains,which not only improved the storage stability of the fermented soymilk,but also improved the organoleptic properties of the fermented soymilk,making both strains potential for the development of a professional fermenting agent for soymilk products.