Dose-Dependent Effects of Pear (Pyrus communis L.) Juice on Kombucha Polyphenols, Antioxidant Capacity, and Enzyme Inhibition

This study investigated the dose-dependent impact of pear juice supplementation on the chemical composition, phenolic profile, and biological activity of kombucha during 14 days of fermentation. Four formulations (0-75% pear juice) were evaluated for changes in (poly)phenols, organic acids, antioxidant capacity, and enzyme inhibition. UPLC-QToF-MS analysis demonstrated substantial remodeling of the phenolic profile in pear-enriched beverages, with marked increases in chlorogenic acid, arbutin, and flavonols. The total phenolic content increased proportionally with juice addition, reaching its highest level in the 75% juice formulation. Fermentation enhanced the antioxidant potential, with FRAP values more than doubling relative to the control. Pear supplementation also enhanced the inhibitory activity of key metabolic and neuroactive enzymes, including α-glucosidase, acetylcholinesterase, and butyrylcholinesterase. Principal component analysis linked phenolic enrichment to improved functional properties, highlighting the biochemical contribution of fruit-derived substrates to fermentation dynamics. Overall, the results demonstrate that pear juice acts as an effective bioactive modulator of kombucha fermentation, promoting the release, transformation, and accumulation of phenolic compounds and enhancing the antioxidant and enzyme-inhibitory potential of the beverage. These findings provide mechanistic insights into fruit-tea co-fermentation and support the development of phenolic-rich fermented beverages with improved nutritional quality and health benefits.