Phenolic compositión of the grapes of the main red Vitis Vinifera varieties cultivated in Uruguay

Abstract

This paper shows the results of an essay on the phenolic composition of Tannat, Cabernet-Sauvignon and Merlot grapes carried out during three years (2001-2003). The vineyards considered were located in the south of Uruguay, and they presented different cultivation situations in order to obtain grapes representatives of the regional diversity. The grapes analysed were sampled in the vintage and the base composition, polyphenolic potential and anthocyanic composition were determined. Tannat berries presented the highest seeds percentages (4,9 % ± 0,5) while the mean weight (1,9 g ± 0,1) was significantly higher with relation to the others. The grapes of this variety had the highest sugar contents (233,9 g/L ± 18,4), total acidity (5,2 g/L ± 0,7), total polyphenols (I.P.T.: 87,9 ± 17,6), total anthocyanins (2758,3 mg/L ± 810,7) and extractable anthocyanins (1344,2 mg/L ± 393,2), and the lowest pH values (3,37 ± 0,07). They also had the highest proportion of anthocyanins in forms of non-acylated glucosides (74,6 % ± 2,7), petunidin (16,6 % ± 1,1) and delphinidin (12,4 % ± 1,8). CabernetSauvignon grapes had the highest skins percentages (11,0 % ± 1,2), the lowest mean weight of the grain (1,5 g ± 0,1) and the highest proportions of anthocyanins such as acetylated glucosides (32,1 % ± 1,3) and malvidin (72,9 % ± 1,8). Merlot grapes presented the highest proportions of anthocyanins in forms of coumaroyl glucosides (9,6 % ± 1,4) and peonidin (11,6 % ± 1,2). The effect of the production year on the polyphenolic composition of the grapes was very important, reflecting the impact of the climatic conditions on the synthesis of these compounds.