Astringency and Lubrication of Polyphenol Systems under Dynamic Salivary Replenishment

Polyphenol–saliva interactions disrupt mucin-mediated lubrication and induce astringency, yet most models neglect dynamic salivary replenishment. Here, a stepwise artificial saliva (AS) addition model was developed to compare tannic acid (TA) and (−)-epigallocatechin gallate (EGCG), with or without xanthan gum (XG). Four systems (TA–AS, EGCG–AS, TA–XG–AS, EGCG–XG–AS) underwent sequential AS replenishment and were characterized using colloidal, spectroscopic, tribological, and electronic tongue analyses. TA–AS progressively formed larger aggregates and exhibited the highest friction, whereas EGCG–AS generated smaller particles and showed lower friction at intermediate stages. In XG-containing systems, TA–XG–AS formed ternary networks with mucin, stabilizing lubrication and reducing astringency. EGCG–XG–AS primarily enhanced film retention with limited aggregation. Spectroscopy and molecular docking suggested stronger TA–mucin interactions, whereas EGCG interactions were more reversible. Overall, polyphenol structure and XG modulation under dynamic replenishment governed mucin lubrication and astringency attenuation.