Sterile Beer Filtration

Background:

The brewing industry has recently experienced phenomenal growth in small and local breweries called micro-breweries or brew pubs. Brew pubs, brew comparative small volumes of beer for consumption in on site restaurants. Sometimes they additionally supply small KEGS for the take home draught market. Since these tasty, craft beers are consumed shortly after the brewing process, the only filtration required is for clarification (removal of yeast and brewing sediment). This is achieved with a small filter press.

As the popularity of the brewer’s beer grows, the brew pub expands its operation by marketing to local restaurants, stores and even outside the local community. At this point two changes occur; 1) the establishment becomes know as a micro-brewery and 2) it becomes necessary to stabilise the beer.

Stabilisation is the process by which beer spoilage organisms (bacteria) are removed. This is necessary to preserve the beer taste over an extended time period. All beers contain bacteria such as lactobacillus and pediococcus, which if not removed alter the taste of the beer. These bacteria are not harmful, but simply change the taste. Stabilisation in large breweries is accomplished by heat pasteurisation. In micro-breweries, stabilisation can be achieved with membrane filtration.

Case Study:

In the brewing process, speciality grains (wheat, barley, rice etc.) are mixed with hops and water. Yeast is added to begin fermenting the grains to alcohol. Following fermentation, the beer is separated from the grains and aged to develop the desired flavour. It is then filtered with a filter press using filter sheets ranging from 1 to 10 microns or as required. Some wheat beers are not filtered.

For beers requiring stabilisation (also called cold filtering), the beer is filtered through a two stage filter system. The first stage contain cartridges rated at 1µm absolute. These are PMT Glass-Mate pleated Borosilicate microfiberglass cartridges and act as pre-filters for the second stage. The second stage utilises PMT PS Ultra-Pure Polyethersulfone micro-porous membrane cartridges rated at 0.45µm. These effectively remove all beer spoilage organisms. Both pre-filter and membrane cartridges are contained in PMT’s T-Style filter housings which are also suitable for gaseous product applications. The number of cartridges required is dependant on the filling rate required. The accompanying table provides a brief recommended sizing together with part numbers.

It is also important to filter the incoming water to maintain a quality, consistently flavoured beer. Incoming water should be filtered with PMT MBC melt blown depth cartridges rated at 20µm absolute. The incoming water filters should be sized to accommodate 11 - 19 LPM per 10" MBC cartridge length.

Media:

- Incoming water: Melt blown depth cartridge / MBC20
- Pre-filter cartridge: Glass-Mate pleated polypropylene / PMG010
- Final filter: PS Ultra-Pure Polyethersulfone membrane / PSRB