Beer Clarification and Stabilization Filters
The figure above shows an abbreviated process from aging through packaging. The filter functions noted are briefly described. More detailed descriptions can be found by clicking on the application links in the menu to the right.
Immediately after the fermentation and aging process is completed, the beer is filtered to remove the large quantity of yeast and hops that have created the brewmaster’s desired taste and color. However, depending on the type of bulk filtration used, there may be DE particles and yeast and hops particles remaining. The trap filter removes most of these and is the first step in stabilizing the beer.
Trap filtration (housing 1 in the figure) is performed using depth filtration media. The kind of media chosen is determined by the particle load of the beer at this stage of production. If the initial bulk filtration has removed most of the particles, then standard depth filters can be used. If the initial filtration is designed in a way that allows more particles to pass, then pleated depth media filter cartridges with a larger surface area are the best choice.
The first step in filtration just before packaging is the removal of sediment, suspended particles and bacteria for initial stabilization of the beer. Removing these particles and larger organisms reduces the amount of material that could create off flavors and aromas. The housing marked “3” in the figure shows the location of this filter just before the final stabilization filter. In addition to removing unwanted materials, the clarification filter protects the final filter from becoming overloaded and fouling prematurely.
As with the trap filters, depth filtration media is often used for clarification. Pleated fiberglass media is most often chosen because of the high flow rates the media allows and the ability of fiberglass media to efficiently remove large amounts of particles.
Immediately before the beer is bottled, the final filter removes spoilage organisms so that the beer will have long shelf life and can be stored at room temperature. If the correct filter is chosen, a beer with clean color and texture is delivered to consumers. The key is choosing a filter designed to allow flavor elements and color to pass while capturing the bacteria that could cause spoilage.
Filters used for this final step are usually membrane filters with 0.45µm or 0.65µm pore sizes. The filters are designed with membrane structures that will capture the bacteria, but allow desired color bodies and flavor elements to pass. Each brewer chooses based on testing and the nature of the organisms that must be removed. Critical Process Filtration partners with brewers to test and validate the performance of filter system designs and to create filtration systems that produce the best beer in the most cost-effective way.
Brewing processes limit the exposure of the aged beer to normal atmosphere to reduce the risk of growth of undesired organisms and possible oxidation of some flavor elements. Normal air is replaced in tanks with process gases – usually carbon dioxide. As the tanks are filled or emptied, the carbon dioxide “blanket” is either forced out or pumped in.
As the beer is bottled, CO2 is injected into the beer for the carbonation level desired. The CO2 also is used to assure that there is little to no oxygen in the bottle that can contact the beer and create the potential for oxidation or mold growth.
Filters (housings marked "2") assure that no particulates or bacteria are carried by the CO2 gas to the wine. In most facilities, hydrophobic 0.22µm membrane filters are used to make sure all bacteria are removed.