Anwendung der Membrandestillation zur teilweisen Alkoholreduktion in Weinen der Sorte Grüner Veltliner

Application of Membrane Distillation for Partial Alcohol Reduction in Grüner Veltliner Wines. The objective of this study was to evaluate whether membrane distillation using hydrophobic membranes is a suitable method under Austrian conditions for reducing the alcohol content of high-alcohol wines and thereby restoring the typical fruity-fresh flavor profile. To this end, early- and late-harvested grapes of the Grüner Veltliner variety were fermented both without enrichment (10.9% vol and 12.1% vol, respectively) and with enrichment to 13.3% vol and 14.3% vol, respectively. The enriched wines were subsequently dealcoholized in steps of 0.7% vol, up to a total reduction of 2.1% vol. During alcohol reduction via membrane distillation with hydrophobic membranes, the effect of saturating the stripping water with nitrogen or carbon dioxide on product quality was also investigated. It was found that carbon dioxide resulted in wines with markedly more fruity and fresher characteristics. Chemical analyses showed that sugar and acid concentrations remained unaffected by membrane distillation. However, reductions were observed in ethyl acetate (14–44%), methanol (6–28%), and higher alcohols. The extent of reduction in volatile compounds was proportional to the degree of dealcoholization but did not negatively affect quality. Sensory evaluation was conducted by officially trained wine tasters using the 20-point scoring system. In all cases, the dealcoholized wines produced with CO₂-saturated stripping water received the highest ratings—specifically, the early-harvested, enriched Grüner Veltliner (initial alcohol content: 13.3% vol) reduced to 12.5% vol, and the late-harvested, enriched Grüner Veltliner (initial alcohol content: 14.3% vol) reduced to 13.5% vol. Descriptive sensory analysis also rated wines with an alcohol reduction of 0.8% vol to 1.5% vol very highly in terms of fruity aroma and flavor, varietal typicity, and overall impression, as confirmed by principal component analysis. Thus, membrane distillation with hydrophobic membranes can be considered an excellent option for modern, future-oriented alcohol management, due to the high product quality achieved, low capital and operational costs, and ease of use.