Sterile filtration of beer.
The paper discusses the relative merits of different filtration processes in terms of efficiency, avoidance of harmful effects on beer quality, the possibility of automation, etc. The principal methods are (1) sheet filters, which are very sensitive to high pressure, require either long pre and post runs or a complicated flushing process with carbon dioxide enriched water, and are difficult to automate (2) double kieselguhr filtration, using two filters each with a different type of kieselguhr, the second being fine enough to eliminate all bacteria (this process can be fully automated and involves no pre or post runs and minimal oxygen pickup), and (3) ceramic filtration, which also produces a sterile filtrate from beer which has been previously filtered with kieselguhr and is now widely used as an alternative to pasteurisation. To enhance the colloidal stability of the beer, PVPP can be added following primary filtration and removed after four minutes by means of a second filtration, preferably with a horizontal kieselguhr filter. With the proper equipment and procedures, over 99% of the PVPP can be recovered for later use. This process does not affect flavour in any way and can improve foam stability and (sometimes) lighten the colour slightly. The treated beer retains its colloidal stability for at least 8 to 12 months. When combined with rigorous standards of hygiene, careful selection of raw materials and well run process control, the filtration procedures described allow the brewer to meet the highest standards of quality and stability.
Keywords : automatic beer ceramic equipment kieselguhr PVPP quality shelf life sterile filtration