The practice of partial defoliation in vineyards has as main objectives increase sunlight and ventilation for the fruit, aiming to improve color and maturity in red grapes and helping to reduce fungal diseases, which should result in better wine quality. The main aim of this research was to evaluate the effects of partial defoliation on the quality of Cabernet Sauvignon grapes and wines from Dom Pedrito, on the southwest of Rio Grande do Sul state, Brazil. The grapes were harvested in March 2008 from a commercial vineyard planted in the trellis system. The defoliation intensity was of 20% and performed only on the side of the vineyard that received the morning sun and when the berry was in the pea-size. The musts were fermented in small lots, in triplicate, with temperature control and remained on the skins for eight days. The results showed that musts of the treatment with defoliation had lower values of pH and higher total acidity. The phenolic content of grape skins and wines was significantly higher for those submitted to defoliation. The defoliation also resulted in wines with greater color intensity, anthocyanins, extract content and reducing sugar, and lower nitrogen content. In wines, there were no significant differences between treatments for total and volatile acidity, pH, alcohol, density, reducing extract and potassium content. As a conclusion, these results might suggest that partial defoliation, as it was done in this vineyard, improves wine quality.
enology; Vitis vinifera; polyphenol; handling; quality