Differentiation between Tannat, Merlot and Cabernet-Sauvignon Uruguayan wines according their global polyphenolic composition

The colour and polyphenolic composition of Tannat, Cabernet-Sauvignon and Merlot red wines elaborated at a reduced scale in the south of Uruguay in 2001, 2002 and 2003 was carried out. The colour and polyphenolic composition of the wines was evaluated through different spectrophotometric indices. Tannat wines gave the highest total content of polyphenols, anthocyanins, catechins and proanthocyanidins. They also had the highest proportions of ionised anthocyanins and the most polymerised and condensed tannins, as well as the highest colour intensities, the highest proportions of red colour and the lowest yellow colour. The year of production was very important, as far as the polyphenols concentrations, values of the polyphenolic indices and colour of the wines are concerned. A Discriminant Canonical Analysis including all the indices of polyphenolic composition differentiated all the wines according to the grape variety. Tannat wines were particularly differentiated by the polyphenolic concentration, whereas Cabernet-Sauvignon and Merlot wines were differentiated specially by the characteristics of the tannins. A Discriminant Canonical Analysis confirms that the reactivity and the polymerisation of the trannins are the variables that better differentiates wines of 2001 from the rest. Wines of 2002 differentiate from the others especially due to the total polyphenolic concentration, whereas 2003 wines due to the characteristic of the tannins