Color preservation of black rice wine through copigmentation stabilization: Structural differences among phenolic acids, pigment transformation, and underlying mechanisms.

Color deterioration in black rice wine is mainly caused by anthocyanin (ATC) degradation during storage. To delay it, phenolic acid copigments were added and their effects on color, ATC stability, and flavor were evaluated, with a cyanidin-3-O-glucoside (C3G) model used to clarify the mechanisms. Phenolic acids showed distinct effects. Protocatechuic acid (PA) and syringic acid (SA) improved ATC retention and delayed degradation. In contrast, sinapic acid (SIA), ferulic acid (FA), and caffeic acid (CA) did not improve initial ATC retention, but promoted the formation of stable pyranoanthocyanins during storage and retarded late-stage color deterioration. Gallic acid (GA) showed limited protective effects. In the model system, protection of C3G stability followed the order SIA and FA > CA and PA > SA and GA, mainly through non-covalent interactions, especially hydrogen bonding and π-π stacking. These findings provide a basis for improving color stability in black rice wine and other ATC-rich fermented foods.