Climate has a huge influence on the ripening of grapes and therefore on the composition of any wine made from them. Wines from regions with high mean temperatures where water is scarce can suffer imbalances such as an excessively high alcohol content and low acidity, making it difficult to turn out a high-quality product. Work is now underway, however, to develop methods of processing very ripe grapes in order to produce red wines with a standard alcohol content (12.5-13.5% v/v). The use of metabolic blockers that redirect the glycolytic pathway in yeasts is one of the most interesting possibilities. The present work investigates how furfural, a well-known aromatic aldehyde with metabolic inhibitory effects on Saccharomyces, can be used to modify alcoholic fermentation in winemaking. The use of this compound led to a significant reduction in the final alcohol content of certain experimental fermentations. When furfural was added at the beginning of fermentation, a maximum reduction of 0.37% v/v alcohol was achieved after the addition of 10 mg/L, and of 0.6% v/v after the addition of 50 mg/L. The natural aromatic profile of the fermentation product suffered no negative variations. The intensity of the effect of furfural on fermentation with respect to the moment of its addition was also studied. Additions made later in fermentation or additions made periodically also inhibited alcohol production, in some cases more so than when added at the beginning of fermentation. The effects of furfural on alcohol production were variable depending on the yeast strain used. Variation of the pH between 3.2 and 3.8 and of temperature between 18 and 25 °C did not modify the intensity of furfural's effect on alcohol production. © 2011 Springer-Verlag.