In previous years we developed a method to assess tannin binding by grape berry cell walls. Using this method during the 2006 season, we studied tannin binding by the cell walls of skin and pulp from five different varieties of wine grapes grown in the Davis experimental vineyard: Cabernet Franc, Sauvignon blanc, Cabernet Sauvignon, Merlot, and Refosco. Among the varieties studied, tannin binding by the skins was found to be dependent on the amount of skin cell wall material produced by the fruit rather than differences in the binding capacity of the material. This is an important result because it indicates that skin cell wall mass should be considered along with berry size in thinking about the relative tannin extractability among different varieties. The way in which the skin cell wall mass varies with cultural conditions or vintage might be an important consideration in understanding the level of tannins extracted during winemaking. We also measured the amount of tannin in the skins and seeds of each of the varieties listed above. This was done so that we could compare the tannin binding capacity of the cell wall material with the amount of tannin in the skins and seeds of the fruit. By comparing the tannin binding capacity of the skin and mesocarp with the amount of tannin in the fruit we found that the cell wall material has the potential to bind from 55 to 140%of the tannin in the fruit at harvest. We also studied Dijon clones of Pinot noir from five vineyards in California and found that the cell wall material had the potential to bind from 43 to 70%of the tannin in the fruit. The work is useful because it can give us an idea of how important the binding of tannins by cell wall material might be in the extraction process during winemaking, but at this point we must be very cautious with our interpretation. For example, the assays to determine binding potential were conducted using a fixed concentration of skin tannin from Cabernet Sauvignon. The actual amount bound will depend on several variables including the nature of the tannin in the fruit and the alcohol level in the final wine. Furthermore, elevated temperatures lead to more tannin release from cell walls and these experiments were all conducted at room temperature. Despite these and other caveats this analysis serves to underline the importance of berry cell walls in the extraction phenomenon.
/wp-content/uploads/2017/09/AFV-Header-Logo.png 0 0 AVF /wp-content/uploads/2017/09/AFV-Header-Logo.png AVF2006-10-16 13:12:352017-10-16 13:13:19Identification of Factors that Influence the Level of Tannins and Polymeric Pigments in Grapes and Wines