Membrane contactor process to reduce ethanol in wine: volatile compounds and stable isotope ratios changes

The reduction of ethanol level in wine is nowadays a notable topic in wine production. There are many different reasons: climate change, health and social matters, wine quality. Many different techniques are available in wine industry to reduce high ethanol content in wine. Among theme contactor membranes, are certainly more efficient and common. We have studied the effect of this practice on the wine quality, aromas compounds and stable isotopes composition. A pilot and industrial plant equipped with the membrane contactor system were used in the study of several white and red wines dealcoholisation. In both scale experiments we have observed changes for several classes of aroma compounds, even if these changes are not in perfect correlation with sensorial evaluation carried out. In addition is observed a variability in aromas variations for each aroma compound and wine variety. We have in particularly studied the modifications on isotopes ratios. We have tested the process using waters with different δ18O ratios, or wines, in different osmotic conditions for both compartments. Modifications of up to 1‰ for 2 %v/v and of up to 4‰ for 8 %v/v ethanol removal were encountered. It is very important to note that the δ18O ratio changes are not only due by a water osmotic transfer through the membrane. The δ18O decrease, is even depending by the δ18O value of the extracting water solution. These variations must be taken into account when these parameters are evaluated to considered dealcoholised wine traceability