Abstract: This study selected peach, citrus and apple pectins to construct liquid composite systems consisting of pectin, anthocyanin and polyphenol, which were systematically analyzed for apparent color, spectral characteristics, anthocyanin content, polyphenol composition and content to elucidate the effects of different pectins on the coloration characteristics of the composite system. Results demonstrated that all three pectins at 0.1% concentration competed with polyphenols for binding to anthocyanin, enhancing the composite system’s apparent color and color stability after ultrasound treatment. The pectin-anthocyanin interaction was dependent on methyl ester groups. Peach pectin, characterized by broad molecular mass distribution (polydispersity index = 4.17) and short-chain dominance (mn = 3.92 × 104 g/mol), exhibited strong anthocyanin interaction, effectively stabilizing the anthocyanin content and altering the chromophore content, and finally causing the system to exhibit a stable deep pink color. Citrus pectin, with its large molecular mass (mw = 30.85 × 105 g/mol) and loose conformation (Rz = 170.60 nm), only weakly stabilized anthocyanins, primarily through physical encapsulation, having no significant impact on the apparent color. Apple pectin, featuring compact structure (Rz = 39.50 nm) and low molecular mass (mw = 1.20 × 105 g/mol), had a minor restricting effect on the molecular motion of free polyphenols after competitive binding to anthocyanins, leading to polyphenol oxidation and chromophore structural modifications, and finally imparting a dark brown color to the system. These findings provide theoretical and technical foundations for developing stable anthocyanin-based food systems through rational pectin selection and structural modulation.

Key words: pectin; anthocyanin; polyphenol; coloration; stability