Interfacial and colloidal drivers of wine drying astringency: the role of wine–saliva aggregates

Astringency in red wine is associated with lubrication changes driven by tannin-saliva interactions, yet the physicochemical basis of astringency subqualities remains unclear. Focusing on drying, a key quality-related subquality, we examined whether wine-saliva aggregates can contribute to lubrication stability rather than only increasing friction. Red wines spanning non-drying to highly drying profiles were mixed 1:1 with unstimulated human saliva. Film thickness and friction were measured under controlled, oral-inspired sliding conditions, and mixtures were centrifuged to obtain soluble (supernatant) and insoluble (pellet) fractions characterized for colloidal stability, interfacial wetting, turbidity, viscosity, and macromolecular composition. Lower drying was associated with thicker films and lower friction, with more stable, entrainable supernatants showing more negative zeta potential, smaller colloids, higher suspended turbidity, and greater polysaccharide support. Overall, the results support a supernatant-centric view in which aggregate functionality and morphology relate to drying subquality, suggesting routes to soften mouthfeel without necessarily reducing phenolics.