Anti-Browning and Prebiotic Effects of White Tea Extract on Fresh-Cut Lotus Root

The enzymatic browning of fresh-cut lotus root, mediated by polyphenol oxidase (PPO), severely limits its shelf life and commercial value. This study investigated the molecular mechanism of lotus root browning and evaluated the prebiotic potential of lotus root treated with white tea (WT) extract. In the browning pattern of fresh-cut lotus root slices, L* and b* values exhibited the most rapid changes within the first 6 h of browning, whereas the a* value increased notably after 24 h. The PPO responsible for this browning process was identified as sequence D6C6L2, and its three-dimensional (3D) structure was established. The catechin and caffeic acid were identified as the specific substrates of PPO with lowest K _m and highest affinity, and molecular docking further revealed that these two substrates bound to the active sites of PPO via 8 and 5 hydrogen bonds, respectively. Based on these mechanistic insights, white tea (WT) extract, rich in flavanol alkaloids, was applied and found to effectively inhibit PPO activity and delay browning. In an in vitro fecal fermentation model, lotus root treated with WT extract enhanced the diversity of gut microbiota, reduced the Firmicutes/Bacteroidetes (F/B) ratio, and enriched the intestinal probiotics Bifidobacterium. KEGG analysis revealed that WT extract modulated carbohydrate metabolism and glycan biosynthesis pathways, suggesting potential prebiotic benefits. This study provided a scientific foundation for the development of lotus root products with both fresh-keeping characteristics and probiotic functions.