Changes in grape seed, skin and pulp condensed tannins during berry ripening: effect of fruit pruning

the purpose of the present work was to study the evolution of condensed tannins according to their degree of polymerization in seeds, pulp and skins, along the maturation using cabernet sauvignon and tinta roriz (vitis vinifera l.) varieties. additionally for this study a witness of each variety was compared with two modalities of fruit pruning, one of 50% and another one of 75%. quantitative changes in the condensed tannins with different degree of polymerization were measured using fractionation on c18 sep-pak cartridges followed by reaction with vanillin, and also by hplc. the results showed that for both two varieties and respective modalities, the concentration of condensed tannins (whatever the degree of polymerization) in any part of grape berry (pulp, seeds and skins) were gradually decreased throughout the ripening period. at harvest, several major analytical parameters of grape berries of the two varieties and for two modalities were not significantly changed. however, significant difference was observed in condensed tannin levels between the control and the pruning modalities.