α- and β-Casein Differentially Protect Anthocyanins from Three Red Grape (Vitis vinifera L.) Cultivars During Simulated Gastrointestinal Digestion.

Grapes are valued for their high anthocyanin content, but the biological efficacy of these compounds is limited by their low digestive recovery. This study evaluated whether milk caseins improve the digestive recovery of anthocyanins from three red grape (Vitis vinifera L.) cultivars. Anthocyanins were profiled by HPLC-DAD-ESI-MS, total phenolic and flavonoid contents and antioxidant capacity were determined spectrophotometrically, the effect on cell viability was assessed on B16-F10 murine melanoma cells, and the digestive recovery of anthocyanins was measured after standardized static in vitro digestion (INFOGEST protocol) with and without α- or β-casein. Thirteen anthocyanins were detected, with malvidin-3-O-glucoside predominating in all cultivars. Fetească Neagră showed the highest total phenolic content (535.01 ± 38.43 mg gallic acid equivalents/100 g fresh weight), flavonoid content (202.52 ± 30.61 mg catechin equivalents/100 g) and antioxidant activity, and its extract reduced melanoma cell viability in a concentration-dependent manner, with viability remaining above 50% over the range tested. Total anthocyanin recovery during digestion decreased from 43.29-46.22% after the gastric phase to 8.82-12.25% after the intestinal phase. α-Casein significantly increased these values to 53.48-55.84% and 15.58-24.74%, respectively, in all cultivars. β-Casein had no significant effect in the gastric phase and was effective only in Pinot Noir after the intestinal phase (10.51% to 19.10%). α-Casein thus limited the intestinal degradation of grape anthocyanins, while cultivar composition determined the extent of the effect.