Improved in vitro digestive stability of epicatechins in green tea infusion fermented by kombucha SCOBY

The functional potential of green tea infusion appears limited by the gastrointestinal instability of epicatechins. This study investigated the effect of kombucha fermentation on the in vitro digestive recovery of epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG). Green tea infusion was fermented for 7 days with a symbiotic culture of bacteria and yeasts (kombucha SCOBY) composed of Brettanomyces bruxellensis, Komagataeibacter rhaeticus, Gluconobacter oxydans, and Levilactobacillus brevis , and subsequently subjected to simulated gastrointestinal digestion. Epicatechin profiles were analyzed by HPLC before and after digestion, with non-fermented infusion serving as the reference. Fermentation resulted in a minor loss of total epicatechins (5 %) but caused a significant increase in EGC content. Most importantly, total epicatechin digestive recovery was substantially higher in kombucha (63 %) compared to the non-fermented green tea infusion (29 %), with the greatest improvements observed for EGCG and EGC. FRAP and TPC analyses were used to evaluate the stabilizing effect of the fermented matrix. Together, these findings enhance our understanding of the health-promoting potential of kombucha beverages.