The Beer Brewing Process – Step 6 : Filtering

The final step in the beer brewing process for most mass produced beers  is filtering.  Filtering is polishing up the finished beer and making sure that it remains stable so that when it reaches the shelves and the stores and is exposed to light and other environmental factors, it doesn’t change in taste, color and body.  However, not all beer is filtered.  Some Australian breweries prefer to leave their beer with some of its “imperfections” intact to give the beer its natural character and uniqueness.

Filtering beer depends on the quality of the beer that the brewer wants to produce.  Rough Filtration means that much of the bigger sediments, like hops and grain particles, that remain in the beer due to fermentation are removed.  The beer that remains is a bit cloudy but clearer than unfiltered beer.  Fine Filtration means a tighter filter which results in a much clearer beer, compared to beer that only passes through rough filtration.  Sterile filtration removes all microorganisms and can even result in removing the carbon from the beer.

Filtering is usually done by using pre-made sheet filters, with specific sizes, to enable breweries to fine tune their beer filtration.  Usually the sheets are placed in the filtering frame and allow the beer to flow through them.  The first pass is usually intended to remove the bigger sediments, so this sheet filter is usually made with loose holes.  This type of filter is used for rough filtering.  A second pass is initiated if fine filtration is required and this sheet is usually made of tighter holes to capture smaller sediments within them.  If the sheets get clogged over time, it is necessary to flush them.  If flushing doesn’t work, then the sheets need to be replaced.

Another method is a little more complicated so it’s used mainly by commercial brewers. It makes use of a powder material that is mixed with the beer.  Common materials include perlite and diatomaceous earth or kieselguhr.  The particles and sediments in the beer get trapped in the pores or get absorbed in the kieselgurh so that when the beer is filtered through screens, the sediments within the kieselgurh also pass through.

When the brewers are satisfied with the quality of the beer after filtering, then there is nothing else to do except bottle, can or keg the beer and launch it from the brewery and into the stores.