Correlation between Skin Cell Wall Composition and Polyphenol Extractability of Pinot noir and Cabernet Sauvignon Grapes

The composition of skin cell wall material from Pinot noir and Cabernet Sauvignon grape berries from four different regions in California were investigated to determine relationships between cell wall composition and phenolic extractability observed under winemaking conditions. Multiple vineyards (sites) per region were studied. Cell wall composition analysis included the determination of total soluble sugars, proteins, non-cellulosic glucose, cellulose, lignin, lipids, total polyphenolic content, soluble polysaccharides, and uronic acid, as well as the isolation efficiency. Results indicated that cell wall material (CWM) composition is mainly site-specific with some impact due to variety and little to no impact due to the growing region. Grape phenolics analyzed included monomeric flavan-3-ols, anthocyanins, polymeric phenols and polymeric pigments and could be used to distinguish between varieties. Grapes grown in the same region exhibited similar phenolic extractability indicating a significant impact of the growing area as well as a synergistic effect between CWM composition and grape phenolics. CWM composition analysis indicated that demethylation of pectin favored the release of phenolics, while lignin content correlated negatively with the phenolics extracted. Proteins showed a negative correlation with polymeric phenols whereas no correlation was found with polymeric pigments. Anthocyanin extractability was highly impacted by its content within grape skins, more so than other phenolics that are present in both the skins and seeds.