Before the experiment is started, it is necessary to wash the membrane distillation system with demineralized water or fresh tap water by pouring the water in the feed tank and turning on the circulation pump. The washing is done for about 20–30 min and then the membrane distillation system is dried until all of the water pours out.
The process is conducted by varying operation conditions both feed pressure in the feed side and vacuum pressure in the permeate side. In the feed side, the feed tank is at room temperature. Beer is pumped into the membrane module by varying the pressure from 2 to 3 bar (gauge). Meanwhile, in the permeate side, permeate stream is at vacuum condition by varying vacuum pressure from 490 to 660 mbar. The vapor outlet is then condensed in a chiller system (4 °C). Because water is also permeated through the membrane, the other components of beer will increase in concentration. By assuming no other beer component but ethanol permeates through the membrane, we must add some makeup water to the feed tank until the initial beer volume is reached in order to maintain the concentration of other components in dealcoholized beer.
In order to identify and analyze the concentrations of various components in both permeate and retentate stream, a high performance liquid chromatography (HPLC) method is used with HPLC Waters system and Aminex HPX-87H column. The eluent used for HPLC analytical method is sulfuric acid (H2SO4) with 0.6 mL/min flow rate. The operation pressure for HPLC is 988 psi, and the internal and external (heater) HPLC temperature are 40 °C and 60 °C respectively. Quantitative data were obtained by comparing the peak areas of the compounds with those of standards of known concentrations. The experimental samples (both permeate streams and retentate streams) were collected for about 10 mL on the end of each run, stored in a refrigerator with cool condition (±4 °C) and were analyzed using HPLC method.