Multiple-strain Lactobacillus-fermented Soymilk With Antioxidant Capacity And Delicate Flavour

Soymilk(SM)is a kind of high-quality food with high protein content,rich nutritional value,and potential bioactive functions.However,the promotion of soybean milk is limited due to the beany smell and the potential functional characteristics have not been fully stimulated.Fermentation is a common means to improve the bioactive functions and flavors of products,but there are few fermented soymilk(FSM)products on the market.The theoretical research of FSM is also relatively backward.Therefore,this paper takes FSM as the research object,and carried out strains screening according to the antioxidant capacity of Lactobacillus plantarum(LP),Lactobacillus acidophilus(LA),Lactobacillus casei(LC),Lactobacillus bulgaricus(LB)and Lactobacillus helveticus(LH)applied to FSM,Based on the selected strains,the feasibility of FSM with mixed lactobacillus was explored,and the technological conditions of FSM with mixed lactobacillus were optimized.In addition,this paper will explore the feasibility of lactobacillus fermentation to improve the flavor of SM,carried out sensory optimization of FSM,confirmed the best formula,and explored the influence of post ripening on the quality and flavor of FSM.Due to the best formula,explore the storage quality changes of FSM,confirm its shelf life,and establish the shelf life prediction model(SLPM)combined with the chemical kinetics model and multiple linear regression model.(1)The results showed that after fermentation,the p H value of SM decreased from 6.52 of unfermented soymilk(UFSM)to 3.80 of FSM,and the protein hydrolysate increased by 54.84%compared with UFSM,and the content was up to 0.040 mg/ml.The acid production and protein hydrolysis capacity of SM fermented by different lactobacillus were different,It shows that there is a possibility of complementarity among strains.In addition,the antioxidant capacity of SM fermented by different lactobacillus is different.TOPSIS method can be used to comprehensively evaluate the antioxidant capacity.The relative closeness to the ideal solution(TOPSIS score)of LP and LA is 0.73 and 0.65,which are the two strains with the strongest comprehensive antioxidant capacity,while the ABTS clearance rate of LB is 45.48%,which is the only strain that can significantly improve the ABTS clearance rate.In addition,LP,LA,and LB were selected for mixed fermentation in this chapter.(2)The results showed that when LP,LA,and LB were mixed in the ratio of 1:1:1(PAB111),the antioxidant capacity of FSM was the strongest,and the TOPSIS score was up to 0.82,It was significantly higher than the UFSM(0.38).The change of fermentation conditions will lead to the different antioxidant capacities of FSM.In general,the fermentation temperature is 37 ℃,the fermentation time is 12 h,and the inoculation amount is 1.5%.(3)After fermentation,SM will produce richer flavor substances.Different lactobacillus fermentation will produce different kinds and contents of aroma substances.The PAB111 group can produce the most aroma species(23 kinds).The sensory score of PAB111 was optimized by a single factor experiment.The best formula was determined as follows: dilution ratio,fermented soymilk: water: 1:3,sucrose addition: 10%,β-cyclodextrin addition: 0.15%.Then,the effect of after-ripening time on the quality of FSM was explored.It was confirmed that the after-ripening time was 1 day,and its sensory score was 14.69% higher than that of non after-ripening SM.(4)The results showed that during the storage at 4 ℃,the sensory score of FSM was the highest on the 1st day(26.7 points),remained stable on the 1st to 7th days(26.01-26.7 points),and was in the critical point of consumer rejection on the 14 th day(14.73 points),so the shelf life(SL)was 14 days.In addition,through Pearson correlation analysis,the physicochemical and aroma indexes of FSM were correlated with the sensory scores.It showed sensory score was negatively correlated with b* value,diacetyl content,and storage time,and positively correlated with ethyl propionate content.Finally,the SLPM of FSM was established by the dynamic model and multiple linear regression model.The dynamic SLPM takes diacetyl content as the key index,the relative error is only 2.36%;The multiple linear regression SLPM takes b* value,acetone content,and ethyl propionate content as regression indexes.The error range of the predicted storage days is within 1 day.The combination of the two models can calculate the remaining SL available for sale.