Development of a diafiltration-pervaporation process for beer dealcoholisation

Nowadays, worldwide low-alcohol and alcohol-free beer markets are growing rapidly, and this leads to a strong demand of improved technologies for their production. Among the various membrane-based processes, a dialysis in diafiltration mode, with no transmembrane pressure difference, has been chosen as first step of a combined process for beer dealcoholisation which includes a pervaporation stage to recover aroma compounds which are then integrated to the final low-alcohol beer. The results of experimental tests for the optimization of beer diafiltration process using a bench scale unit and two different membranes of cellulose and polyacrylonitrile are shown in this work. A commercial lager beer has been dealcoholized, in a discontinuous diafiltration mode, interweaving concentration and dilution stages, up to an alcohol content lower than 1.2 %vol., which is the residual alcohol content for low alcohol beverages in European countries. Various dialyzing solutions and operating parameters (e.g., temperature, flow rate, volumetric concentration ratio) were tested in order to improve the ethanol removal from the beer. The physical-chemical characteristics of the beer such as pH, electrical conductivity, density and colour and free-phenolic profile, before and after the dealcoholisation process were evaluated. Results showed no substantial differences between the membranes tested for the dealcoholisation process and small differences in the physical and chemical characteristics of beer before and after the treatment.