Effect of pH and Ethanol on Tannin-Polysaccharide Interactions
Aude Watrelot* and James Kennedy
*Department of Viticulture and Enology, University of California,
Davis, CA, 95616-5270 (firstname.lastname@example.org)
Tannins are considered to be the primary group of phenolic compounds responsible for astringency in red wines, with structure variation having an impact on perception. It has also been well documented that wine matrix can influence tannin perception. Ethanol, pH, and polysaccharides are known to affect the underlying process of astringency, or tannin-salivary protein interaction. To improve under-standing of matrix consequences on tannin-polysaccharide-protein interactions, the pH and ethanol concentration of model wines was varied from 3.0 to 4.0 and 10 to 18% (v/v), respectively. Tannins and polysaccharides used for study were previously isolated from red wines. The formation of haze after tannin-polysaccharide interac-tions in different model wines was followed using spectrophotometry at 650 nm. The concentration of precipitable tannin after tannin-polysaccharide interactions in model wines and of mannan-red wine tannin interactions were characterized by a protein precipitation assay using bovine serum albumin. Our results showed that tannin-protein interaction varied as a function of pH, ethanol, and polysaccharide variation. Under the experimental conditions, precipitable tannins increased with pH and ethanol concentration. The effect of pH and ethanol concentration on mannan-tannin and on mannan-red wine tannin interaction was also investigated. Overall the results of this study indicate that tannin perception can be managed to an extent through pH, ethanol, and polysaccharide adjustment.
Funding Support: American Vineyard Foundation