The improvement in stability and coloration effect of gallic acid acylation of anthocyanins and their quantum chemical mechanism

To address the limitations in functionality and stability of current anthocyanin-based smart packaging indicators, this study developed an innovative enzymatic acylation strategy. Through lipase-catalyzed grafting of gallic acid (acylation degree: 9.16%), acylated anthocyanins with excellent thermal stability (1.5-fold extended half-life), photostability (32% higher retention after 48-hour UV irradiation), and pH sensitivity (pH 4-8) were successfully prepared. By combining characterization techniques including Fourier transform infrared spectroscopy, high-performance liquid chromatography, and ultraviolet-visible spectroscopy with density functional theory calculations, it was discovered that diacylation synergistically enhanced molecular rigidity through π-π conjugation and hydrogen bonding networks (electrostatic potential energy reduced by 1295 kJ/mol). Notably, despite the reduction in phenolic hydroxyl groups, the acylated products retained strong antioxidant activity (verified by DPPH assay) due to residual galloyl moieties. This research not only elucidated the intrinsic mechanisms of structure-property relationships but also provided novel insights for developing high-performance natural smart packaging indicators, offering important guidance for food freshness monitoring and the design of stabilized anthocyanin functional materials.