| In this study,8 probiotics including in Lactobacillus casei Zhang,Lactobacillus plantarum P-8,Lactobacillus plantarum P9,Bifidobacterium cinimalis subsp.lactis V9,Bifidobacterium animalis subsp.lactis M8,Bifidobacterium breve BB-X,Lactobacillus rhamnosus M9 and Lactobacillus helveticus H9 with clear source,good probiotic characteristics and health functions were used as experimental strains to prepare for active lactic acid bacteria beverages,which for exploring the fermentation characteristics of compound probiotics and the effects of different fermentation base materials on the antioxidant,antipathogenic and Angiotensin Converting Enzyme inhibitory activity properties of lactic acid bacteria beverages.The volatile metabolites in lactic acid bacteria beverages before fermentation,at the end of fermentation and during storage were quantitatively analyzed by solid phase microextraction coupled with gas chromatography-mass spectrometry.The key volatile flavor substances in lactic acid bacteria beverage were determined by odor activity value.The specific results are as follows:1.Compound probiotics grew fastest in skimmed milk,and the total number of viable bacteria was the highest when the stable period was reached,followed by soymilk and relatively slower in whey.The changes of acidity was basically consistent with the growth curve.The active lactic acid bacteria beverages with three different base materials all have good storage stability,during the storage period,the acidity did not change significantly,and the number of viable bacteria was always above 3×108 CFU/g.2.In terms of a single functional feature of lactic acid bacteria beverages,skim milk beverage has stronger overall antioxidant capacity,SOD activity was significantly higher than the other two groups(P<0.05),whey beverage has the strongest scavenging capacity for·OH,GSH-Px activity was significantly higher than the other two groups(P<0.05),and soymilk beverage has relatively weak overall antioxidant capacity.skim milk beverage and soymilk beverage have stronger overall antibacterial ability,and the contents of phenyllactic acid and 4-hydroxyphenyllactic acid were significantly higher than those in whey beverage(P<0.05).In terms of the inhibitory species of pathogenic bacteria,all the three kinds of lactic acid beverages have stronger inhibiting ability to Escherichia coli.the Angiotensin Converting Enzyme inhibitory activity of skim milk beverage was significantly higher than that in whey beverage and soymilk beverage(P<0.05),and the contents of Val-Pro-Pro,Ile-Pro-Pro and GABA were significantly higher than the other two groups(P<0.05).Val-Pro-Pro and Ile-Pro-Pro were not found in soymilk beverage.lactic acid bacteria beverages of fermentation base material and storage time has an effect on its functional characteristics,and the effect of fermentation base material on its functional characteristics was more significant.The comprehensive scores of functional characteristics of lactic acid bacteria beverages with different base materials during storage period were as follows:skim milk beverage>whey beverage>soymilk beverage.As time goes on,the overall functional characteristics of the three active lactic acid bacteria beverages showed a trend of increase first and then decrease.3.A total of 107 volatile flavor compounds were detected in three kinds of active lactic acid bacteria beverages before fermentation,at the end of fermentation and during storage.The volatile metabolites of lactic acid bacteria beverages with different base materials were obviously different after the complex probiotics fermentation,while the volatile metabolites of lactic acid bacteria beverages with the same base materials changed little during the storage period.heptanal,(E)-2-octenal,2,3-butanedione,2-nonanone,3-methyl-butanol,1-octen-3-ol were the key volatile flavor substance in skim milk beverage.acetaldehyde,3-methyl-butanal,heptanal,(E)-2-nonenal,3-methyl-4-heptanone,2-nonen-1-ol were the key volatile flavor substance in soymilk beverage.After fermentation,the content of hexanal,1-hexanol and other volatile substances causing beany flavor decreased significantly(P<0.05),while acetaldehyde,3-methyl-butanal and other volatile substances giving soymilk beverage good flavor were produced.valeraldehyde,nonanal,decanal,(E)-2-decenal were the key volatile flavor substance in whey beverage.This study provides an important application research basis for the commercial application of compound probiotics and the development and utilization of active lactic acid bacteria beverage products. |
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