Improving fermented milk antioxidant properties by functional enrichment with Vitis Vinifera leaf extract cv Monica loaded in nanovesicles

Kefir is increasingly appreciated for its probiotic-rich composition and health benefits, aligning with the growing demand for functional foods. This study introduces an innovative approach to fortify kefir with grapevine leaves extract, an underutilized viticultural by-product, thereby promoting circular economy practices. The extract, characterized by a high total polyphenol content and remarkable antioxidant capacity, was analysed by HPLC-DAD, which identified caftaric acid, quercetin-3-O-glucuronide, and peonidin-3-O-glucoside as major phenolic constituents. The extract was encapsulated in nanovesicles prepared via a gentle high-shear homogenization method, a milder alternative to sonication that preserves thermosensitive compounds. The resulting nanovesicles exhibited encapsulation efficiencies ranging from 28.8 % to 73.9 % and demonstrated good physical stability. Moreover, they effectively mitigated the degradation of the extract components in simulated gastrointestinal conditions and protected enterocytes from oxidative stress in vitro. Incorporation of the loaded nanovesicles into the fermented drink enhanced its antioxidant activity in a dose-dependent manner without altering rheological properties.