Alternativas vitícolas y enológicas para la reducción del contenido de alcohol y pH en los vinos tintos Tannat

Uruguay is characterized by high interannual climate variability, expressed in fluctuations in temperature and rainfall that directly impact vineyard development and grape ripening. High temperatures and periods of drought have accelerated ripening processes, producing wines with higher alcohol content and pH, but with incomplete phenolic and aromatic profiles. This situation forces the period to be extended, making it difficult to determine the optimal time for harvesting. The objective of this research was to evaluate the impact of pre apical leaf removal and the partial replacement of ripe must with must or wine from unripe grapes on reducing the alcohol content and pH of Tannat red wine, without modifying its phenolic composition and colour. The study was conducted during the 2025 harvest in a commercial vineyard in southern Uruguay. Six groups of ten plants were studied, three of which underwent pre-apical leaf removal at the beginning of veraison (E-L 36) by manually removing leaves from the seven nodes above the second cluster, while the other three groups were left as controls without leaf removal. The canopy structure, yield and evolution of grape composition were evaluated until harvest. Wines were produced in triplicate for the following treatments: VT (control, traditional vinification), VD (pre apical leaf removal), VSM (replacement of 20% of ripe must with unripe grape must) and VSV (replacement of 20% of ripe must with unripe grape wine). The physicochemical parameters, phenolic composition, colour and sensory characteristics of each wine were determined by a panel of tasters. The results showed that pre apical leaf removal reduced the leaf area without affecting yield. This technique influenced the accumulation of sugars in the berries, allowing the production of wines with lower alcohol content. The most relevant differences in phenolic composition were observed in the wines, with reductions of more than 15% compared to VT, also affecting colour. The VSM and VSV treatments succeeded in reducing alcohol content and pH. The variations in phenolic composition did not exceed 10% compared to the control. No sensory differences were found between the wines, except in terms of appearance. The tasters showed a greater preference for wines from the VD and VSV treatments. In conclusion, both the viticultural and oenological strategies evaluated represent viable alternatives to produce wines with lower alcohol content. The impact on colour and phenolic composition will depend on the climatic conditions of each harvest, so their application must be adapted to the agroclimatic context of each year.