Aude A. Watrelot,* Delia L. Schulz, and James A. Kennedy
*Department of Viticulture and Enology, California State University, 2360 E. Barstow Ave, MS VR89, Fresno, CA 93740 (awatrelot@csufresno.edu)

The class of molecules that contributes most significantly to overall red wine astringency is condensed tannins. Due to their molecular mass and surface properties, red wine tannin activity and sensory perception can vary depending on composition, conformation, and interaction with macromolecules present in wine, principally polysaccharides. Polysaccharides from yeasts and/or grapes are released during winemaking and influence tannin perception and red wine stability. High performance liquid chromatography (HPLC) and UV/vis absorbance spectrophotometry were used to improve understanding of tannin behavior in the presence of polysaccharides isolated from Cabernet Sauvignon and Pinot noir wines. After characterization of isolated polysaccharides using size exclusion chromatography, it was determined that Cabernet Sauvignon wines were mostly composed of oligosaccharides, in contrast to Pinot noir wines, which contained an increased proportion of arabinogalactan proteins and mannoproteins. Tannin activity in the presence of polysaccharides, as measured by HPLC, was similar to tannins in the absence of polysaccharides, indicating that polysaccharide interaction with tannins is noncovalent. In contrast, when tannin activity was measured in situ using UV/vis absorbance spectrophotometry, activity declined in the presence of polysaccharides. Taken together, the results of this study suggest that it is important to consider both tannins and polysaccharides when investigating red wine astringency and stability.

Funding Support: American Vineyard Foundation, California State University Agricultural Research Institute