Proanthocyanidin Composition of RedVitis viniferaVarieties from the Douro Valley during Ripening: Influence of Cultivation Altitude

The effect of altitude and its related climatic conditions on the proanthocyanidin composition of Touriga Nacional and Touriga Francesa varieties during berry maturation is reported for the 1997 vintage. At berry maturation, low altitude is shown to be an important factor favoring the biosynthesis of higher concentrations of grape-skin catechin monomers ((+)-catechin, (-)-epicatechin, (-)-epicatechin gallate), procyanidin dimers, trimer C1, as well as total extractable proanthocyanidins. The grapes (skin and seeds) of Touriga Nacional were found to be richer in low molecular weight flavan-3-ol compounds, while Touriga Francesa contained higher concentrations of total extractable proanthocyanidins. At harvest, grape-skin dimer content was comprised almost entirely of dimer B1, followed by dimers B2 and B3, whereas C4-C8 linked dimers (B1 to B4) and B2-gallate were the most abundant found in seeds. Dimer B2, which was one of the less important dimers at the early stage of development in seeds, showed a tendency to increase during ripening, while its respective gallate ester (B2-gallate) markedly decreased.