Aude A. Watrelot,* Tonya L. Kuhl, and Andrew L. Waterhouse
*UC Davis, One Shields Ave, Davis, CA 95616 (awatrelot@ucdavis.edu)

The perception of astringency has been characterized extensively through chemistry (complexes between salivary proteins and tannins) and by sensory analysis with trained panels to predict human perception. The physical aspect/human oral physiology of wine astringency perception has not been studied until now, although saliva has been shown to be involved in mouthfeel perception. In this study, condensed tannins were extracted from two red wines (cv. Cabernet Sauvignon and Pinot noir) and added back to them and to a model wine at 0.5 g/L, prior to chemical characterization of their composition by HPLC-DAD after acid-catalysis and by sensory analysis. The chemical consequences of interactions between mucin, poly-L-proline, saliva and red wine tannins were evaluated by turbidimetry and protein precipitation assay. The friction/lubrication properties of lubricant (mucin or saliva) with red wines were measured with a surface force apparatus, including development of a method to mimic mouth lubrication. The mean degree of polymerization of Cabernet Sauvignon condensed tannin, and the haze/aggregates formation with mucin and poly-L-proline were higher than in Pinot noir tannin. The turbidity of saliva and poly-L-proline with tannins added to Cabernet Sauvignon was higher than that of tannins added to Pinot noir wine. The coefficient of friction measured for red wine, with saliva as the lubricant, was higher in Pinot noir than in Cabernet Sauvignon wine. The lower friction of Cabernet Sauvignon is likely due to exclusion of the aggregates and depletion of more polymeric and protein material from the contacting region. The perceived dryness of red wines correlated positively with turbidity measurements with saliva, while the correlation with friction coefficient was much lower, meaning that physical, chemical, and sensorial methods must be used together to get an overview of red wine astringency perception.

Funding Support: American Vineyard Foundation