Fortification of Water Kefir with Gallic Acid: Physicochemical Effects and Antioxidant Capacity in an In Vitro...

Today, consumers are interested in healthier food. Fortifying water kefir (WK) with gallic acid (GA) could enhance kefir's health benefits. The objective of this study was to evaluate the effects of GA-fortified WK (WK-GA) and pasteurization on physicochemical parameters and antioxidant capacity after an in vitro digestion. The results showed that WK-GA had significantly higher (p < 0.05) dry biomass than WK, 9.52 and 9.22 g/L, respectively. No significant differences were found (p > 0.05) at pH and °Brix kinetics. Antioxidant capacity kinetics using DPPH^• and ABTS^•+ showed that WK-GA maintained its antioxidant effect throughout the fermentation process, inhibiting free radicals by 89.9% and 98.6%, respectively. In FRAP, WK-GA reached 14.63 mM TE/mL, while WK had 4.19 mM TE/mL. Furthermore, the antioxidant capacity of the bioavailable fractions decreased in DPPH^• and FRAP, even after pasteurization. However, in the ABTS^•+ assay, the antioxidant capacity of the bioavailable fraction remained at 94% inhibition. These results demonstrate the potential to fortify WK with GA to improve the beverage without altering its physicochemical characteristics, thereby enhancing its antioxidant capacity. This opens the door for future studies examining the positive health effects of GA when used in a matrix like WK.