Composition and cellular localization of tannins in grape seeds during maturation

Cell walls were isolated from seeds of grape berries (Vitis vinifera L.), and proanthocyanidin composition was determined over the course of ripening for different levels of vine water status. During the ripening period the tannins from the cell walls were always more polymerized than those from the inner part of the cell. At maturity this difference becomes more significant compared to véraison, due to a significant increase in the mean degree of polymerization of the cell wall tannins. The tannin composition was typical of grape seed tannins and was quite similar in the two cell fractions studied, but the epicatechin gallate proportion was significantly higher in the cell wall fraction. There were no significant effects of water deficit on composition and polymerization of seed tannins.