Quality Attributes of Low-Alcohol Top-Fermented Beers Produced by Membrane Contactor

The practice of dealcoholization is used nowadays to reduce the alcohol content in beverages, and osmotic distillation seems to be a convenient membrane process due to its mild operating conditions. The focus is on the quality of final beverage which may lack in taste, flavor, and body. The aim of this work was to evaluate the quality attributes of low-alcohol beers, dealcoholized by osmotic distillation and using stripping solutions specific for the beverage composition. Two types of top-fermented beer were used: Weiss beer, with a very fruity aroma and strong phenolic content, and Bitter beer, with a malt aroma. Regarding the stripping solutions, they were obtained by dilution of the original beer with water, in order to limit the volatile compound loss during the process. Moreover, low-alcohol Weiss beer was also produced by using carbonated stripping solutions (i.e., saturated with CO2 at ambient pressure). The results highlighted that color, bitterness, total phenols, and antioxidant activity were unchanged in the low-alcohol beers but volatile compounds were reduced to a different extent. The lower vapor pressure of some volatile compounds (i.e., 2-phenylethanol, aldehydes) can explain their retention in beer. The carbonation of stripping solutions did not significantly reduce CO2 loss, but aldehydes and total alcohols were better retained in low-alcohol Weiss beer. Esters and other volatile compounds were reduced so that the low-alcohol beer may result with a weak sensory profile, which can be compensated by a re-addition of CO2 before bottling.