Cristina Medina-Plaza, Nick Dokoozlian, Ravi Ponangi, Tom Blair, David Block, and Anita Oberholster*
*University of California, Davis, Department of Viticulture and Enology, 595 Hilgard Lane, Davis, CA 95616 (aoberholster@ucdavis.edu)

The phenolic component of red wine is responsible for important elements of the flavor, mouthfeel, and quality of the finished wine. While the origin, concentration, and chemistry of the phenolics in a finished red wine are well known, the fundamental mechanisms and kinetics of extraction of these compounds from grape skins and seeds during red wine fermentation are poorly understood. Berry skin cell walls play a very important role during the winemaking process by forming a barrier to the release of important components impacting aroma and color and by providing a potential adsorption surface. Commercial winery observations that polyphenol extraction levels during winemaking may vary based on grapegrowing region and cell wall composition are a potentially important factor influencing this relationship. In this work, the composition of skin cell wall (CW) material from Vitis vinifera cv. Cabernet Sauvignon and Pinot noir has been studied, aiming to relate the difference in CW composition among varieties with the polyphenol extractability obtained from different regions within California. This study includes the analysis of total soluble sugars, proteins, non-cellulosic glucose, Klason lignin, cellulosic glucose, total polyphenolic content, and lipids, as well as the isolation efficiency. Differences in the cell wall material composition between regions were found for all the parameters studied, especially for protein, non-cellulosic glucose, soluble sugars and polyphenolic content. Multivariate analysis was performed to associate the cell wall material composition to the extractability values. Results showed that the differences in extractability could be due to differences in grape cell wall pectin, cellulose, and protein content, which are a function of the region of grape cultivation.

Funding Support: E&J Gallo Winery