Anthocyanic composition of Tannat grapes from the south region of Uruguay Original Research Article

The anthocyanic composition of Tannat grapes produced in different vineyards in the south region of Uruguay was studied. Two training systems (vertical trellis and lyre) and two pruning methods (Guyot and Royat cordon) in the lyre were considered. A follow-up was carried out, considering 60 plants per treatment, and the vintage was determined according to the traditional indices of maturity. At the moment of the harvest, samples of grapes were taken in duplicate in each treatment and the soluble solids, total acidity, pH, phenolic richness, total potential in anthocyanins and extractable anthocyanin contents were determined. Grapes were frozen and later analysed; skin extractions over 24 h with a solution of 12% ethanol and pH 3.2 were carried out. The anthocyanic contents of the extracts obtained were determined by liquid chromatography. The total potential in anthocyanins of the grapes from the lyre with cordon pruning was significantly higher than the others, whereas the grapes from the cane pruning presented the highest extractable anthocyanins contents. The phenolic richness of the grapes from the lyre (with both pruning systems) was significantly higher than in the vertical trellis. Significant differences in the contents of the anthocyanins and in the anthocyanic profiles of the grapes of each treatment were found. Grapes from the vertical trellis system presented significantly higher proportions of malvidin, coumarylic and acetyl anthocyanins. Grapes from the lyre with cordon pruning presented significantly higher proportions of delphinidin, cyanidin, petunidin and peonidin, and non-acylated glucosides. It can be concluded that the yields and the environmental conditions given by the different vineyards determined important differences in the phenolic composition of Tannat grapes. The anthocyanic profiles of the grapes presented significant differences that might determine important variations in the colour and composition of the respective wines.