Molecular basis of sediment formation in cereal vinegar driven by polysaccharide-protein-polyphenol ternary...

Abiotic sediment formation during aging compromises visual stability and quality consistency of cereal vinegar, yet its molecular basis in acidic matrices remains unclear. Here, Shanxi aged vinegar was investigated as a polyphenol-rich system comprising polysaccharides, proteins, and phenolics. Sedimented polysaccharides were glucose-rich heteropolysaccharides containing arabinose, xylose, and mannose. In reconstructed systems, mannan-wheat bran protein-vanillic acid showed the greatest destabilization, with an instability index exceeding 0.60 under elevated-temperature conditions. Quantitative excitation-emission matrix fluorescence analysis showed that mannan decreased the vanillic acid-associated maximum fluorescence intensity by 42.8%, indicating a pronounced change in its fluorescence environment. In a gliadin-based molecular model, vanillic acid preferentially associated with hydrophobic protein regions and restricted conformational mobility, while the gliadin-mannan distance increased from 21.49 to 38.5 Å, consistent with redistributed protein-polysaccharide contacts. These findings support a polyphenol-associated interaction-reorganization model and provide a multiscale framework for ternary colloidal destabilization under the tested acid-salt conditions.