Metabolomics-based mechanistic insights into antioxidant enhancement in mango juice fermented by various lactic acid bacteria

Lactic acid bacteria (LAB) fermentation can modify the antioxidant capacity of food. This study investigates the impact and mechanisms of various LAB strains (Lactobacillus plantarum NCU116, Lactobacillus acidophilus NCU402, and Lactobacillus casei NCU215) fermentation on the antioxidant properties of mango juice. LAB strains inoculation enhanced the antioxidant activity of mango juice, with metabolomics showing increased in polyphenols and decreased in vitamins and carotenoids, indicating polyphenols as the main contributors. Quantification of polyphenols (free and bound forms) revealed that fermentation decreased bound gallic acid levels while increasing free pyrogallol and 1,2,3,4,6-O-pentagalloylglucose, which mainly contributed to the rise in antioxidant capacity in mango juice. L. acidophilus NCU402 had the highest increase in 1,2,3,4,6-O-pentagalloylglucose (from 918.07 to 1750 μg/10 g), whereas L. casei NCU215 facilitated the greatest release of bound gallic acid (49.29 to 11.77 μg/10 g). Bound polyphenol release may be linked to pectin degradation, with lower galacturonic acid and increased pectinase activity.