Characterizing metabolites and biotransformation in lactic acid bacteria fermented Millennium cherry tomato juice using integrated analytical tools

Fermentation with lactic acid bacteria (LAB) enhances the nutritional value and flavor of food matrices. This study investigated the impact of Pediococcus acidilactici HNU168, Bifidobacterium animalis subsp. lactis HNU329, and their combined fermentation on Millennium cherry tomato juice (MFJ). Fermentation boosted organic acids, total flavonoid content (TFC), xanthine oxidase (XOD) inhibitory activity, and antioxidant activities. Mixed-strain fermentation significantly increased antioxidant activity and lycopene content beyond single-strain fermentation. Non-targeted metabolomics identified 745 differential metabolites, mainly enriched in purine metabolism and phenylpropanoid biosynthetic pathways, facilitating key metabolite biotransformation. Notably, lycoperodine l, 3-(4-hydroxyphenyl) lactate, indole-3-lactic acid, and dihydrocoumarin contents increased significantly. Molecular docking and XOD inhibitory activity confirmed strong interactions between key metabolites and XOD. Also, electronic tongue analysis showed that LAB-fermented MFJ had increased richness and reduced bitterness and astringency. These results illustrate that LAB fermentation improves MFJ's nutrition, bioactivities, and sensory properties, offering potential applications in functional or anti-hyperuricemia foods.