Differentiation of Tannat, Cabernet Sauvignon and Merlot grapes from Uruguay according to their general composition and polyphenolic potential

This paper shows the results of a study carried out during four years (2001-2004). Its aim was thecharacterization of Tannat, Cabernet Sauvignon and Merlot grapes cultivated in the south ofUruguay. The results were evaluated to qualify the enological potential of these varieties of Vitisvinifera L. Typical cultivation situations in the region were included of each variety. The grapeswere analysed at harvest for determination of global composition and polyphenolic potential.Tannat grapes presented very different characteristics in relation to other varieties. Tannat had thehighest percentage of seeds, berry weight, sugar contents, total acidity, total polyphenols, totalanthocyanins, extractable anthocyanins, skin tannins and seed tannins levels. Also, they had thelowest pH values and the highest EA%, corresponding to the lowest extractability of anthocyanins.The effect of vintage on the grape composition was very important, according to the impact of theclimatic conditions in the synthesis of quality components of berries. However, the joint considerationof analytical indexes of base composition, polyphenolic potential and structure of the berry alloweda perfect discrimination of samples of each variety.