Partial Removal of Ethanol during Fermentation to Obtain Reduced-Alcohol Wines

摘要

The demand for wines with lower alcohol content has increased over recent years. There are various techniques for lowering alcohol content, including ethanol extraction from the wine and reduction of sugar content of the musts. The feasibility and potential importance of ethanol extraction techniques during wine fermentation were determined. In 100 L pilot-scale fermentations, 2% ethanol was removed halfway through fermentation, either by distillation under vacuum or by stripping with CO_2. Despite being stressful for the yeasts, none of these treatments had a negative effect on fermentation kinetics. On the contrary, the fermentation rate increased, probably due to the extraction of inhibitory compounds and, consequently, the fermentation was easier to complete. Removing 2% ethanol during the course of fermentation slightly affected the final concentration of compounds derived from yeast redox metabolism (glycerol, acetate) and aromatic molecules. Both treatments lowered the volatile compounds content (by 25% and 45% for fusel alcohol and esters, respectively), but these losses were partly compensated for by synthesis in the second part of fermentation. The final concentrations were thus close to or even higher for glycerol and isobutanol (up to 19% and 32% depending on the treatment, respectively) than those of the control fermentation. In addition, sensory analysis detected no significant difference between wines produced with or without dealcoholization treatment, except for a slight negative effect with stripping. Removing 2% ethanol by stripping or by distillation during the fermentation are promising alternatives for reducing the alcohol content of wine without altering the sensory quality of the product.