Evaluation of physicochemical characteristics, bioactivity, flavor profile and key metabolites in the fermentation of goji juice by Lacticaseibacillus rhamnosus

This study aimed to investigate the changes in physicochemical properties, bioactivities and metabolites of fermented goji juice (FGJ) by Lacticaseibacillus rhamnosus at different fermentation stages. The results showed that Lacticaseibacillus rhamnosus fermentation significantly decreased the content of soluble protein, total phenolic, total flavonoid and total sugar. Meanwhile, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability and the inhibition rate of xanthine oxidase (XOD) activity were remarkably enhanced by Lacticaseibacillus rhamnosus fermentation. Flavor profiles analysis indicated that FGJ produced novel volatile compounds such as 4-methylpentanol and 2-butanol, which provide its distinct aroma. The non-targeted metabolomics analysis showed that the differential metabolites in the FGJ28 vs. FGJ0 group were mainly included 1,7-bis (3,4-dihydroxyphenyl) heptan-3-yl acetate, isoplumbagin, triacetylresveratrol, sulochrin, indole-3-acetaldehyde, etc., which might have an effect on the promotion of the bioactivity of goji juice. These findings will contribute to understanding the biotransformation effect of Lacticaseibacillus rhamnosus fermentation on goji juice.