Oral tribology: Update on the relevance to study astringency in wines

Oral tribology is emerging as a new paradigm to quantify friction and lubrication of food-saliva mixtures in the oral mucosa. Recently, oral tribology has captured research attention in quantifying wine astringency, a characteristic "dryness feeling", which strongly impacts consumer preference. Hence, this paper aims to provide a concise review of oral tribology in the context of wine astringency. Firstly, the important roles of "biolubricant" saliva, salivary proteins and current tribo-pairs used in oral tribology measurements are reviewed. Then, we have discussed the key mechanisms of wine astringency involving polyphenol-salivary protein interactions (hydrogen bonding, hydrophobic interactions), rupture of the lubricating salivary film and oral sensation of discrete particles. Studies employing Stribeck curve analysis and microstructural characterization to understand polyphenol-salivary protein interactions are reviewed. Finally, we highlighted the need for bio-relevant tribo-pairs, simulated oral conditions and tribology-sensory correlation, before such quantification can be used to characterize wine astringency at a commercial level.