Effect of lactic fermentation and matrix on phenolic content, bioaccessibility, and scavenging activity of beetroot beverages

Abstract With the rising interest in fermentation techniques and the FAO’s advice to increase fruit and vegetable consumption to lower disease risk, this study investigates the fermentation of two beetroot beverages: a low-fiber juice and a high-fiber puree-based beverage. The lactic fermentation process enhanced the free phenolic content in both juice and puree-based drink (from 2.37 to 4.83 mg/g and from 2.44 to 6.56 mg/g, respectively) and the antioxidant activity in the beetroot juice (from 19.7 to 45.99%), as assessed by colorimetric assays. The findings reveal no correlation between free phenolic content and antioxidant activity, suggesting that other factors, such as the structure of phenolics or the presence of compounds, like organic acids, play a role in antioxidant activity of beetroot beverages. Notably, although fermentation increased free phenolics, the juice exhibited decreased in vitro bioaccessibility of phenolics after fermentation (from 90.07 to 61.35%), while the puree showed an increase (from 63.99 to 92.14%). These observations highlight the dualistic role of fiber-phenolic interactions during fermentation: acting both as a protector against phenolic degradation and a barrier to intestinal absorption.