Synergistic Enhancement of Phenolic Profile, Color Stability, and Aroma Complexity in Marselan Wine Through Co-Fermentation with Fu Tea

Co-fermentation of tea and wine offers a promising route to functional beverages with enhanced sensory complexity and potential health benefits. We co-fermented Marselan (Vitis vinifera L.) grapes with Fu brick tea (0, 0.5, 1.0, 1.5 g/L), a post-fermented tea containing the probiotic fungus Eurotium cristatum. We systematically examined how tea-derived phenolics modulate wine color and aroma. Fu tea addition progressively decreased alcohol (12.24% → 10.86%) and modestly reduced residual sugar, while volatile acidity remained stable, indicating no adverse fermentation impact. HPLC revealed a substantial increase in tea-derived phenolics; chlorogenic acid nearly doubled and became the dominant phenolic compound. CIELab color analysis showed increased lightness (L) and marked decreases in yellow hue (b) and hue angle (h°). Total phenolic content correlated negatively with h° (r = −0.656, p = 0.0205), suggesting that the overall phenolic load—not any single compound—is associated with the shift toward a more stable brick-red hue. PCA showed that chlorogenic acid contributed to both color (PC1) and phenolic (PC2) variation. GC-MS revealed substantial increases in esters and higher alcohols, and the emergence of 1-octen-3-ol, a characteristic metabolite of E. cristatum. C6 compounds associated with herbaceous aromas decreased significantly. Fu tea co-fermentation thus enhanced wine color stability and aroma complexity through a multifaceted phenolic network. Under our conditions, 1.0 g/L Fu tea gave the most favorable balance of color stability and aroma complexity. These findings provide a preliminary theoretical basis for developing tea-wine products, though further mechanistic studies are needed to establish causality.