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What is the process of cold filtering?

To many American beer drinkers in the post-World War II era, the elite beer was a bright, clean, crisp, and golden brew with no haze whatsoever, and drunk at the coldest temperatures. This trend accelerated as Lager beers became omnipresent and since beer was being shipped farther from its point of origin, making filtering important to stabilize the beer and extend its shelf life.

Although ALL beer filtering is done cold, the expression “cold filtering” describes a specific filtering process where the beer is cooled enough so that the protein molecules can clump together and be easily removed from the final product. Many breweries substitute heat pasteurizing with cold filtering. By cold filtering, beer can travel through a filter that effectively eradicates the fine suspended yeast particles and halts fermentation.

The process of cold filtering does not necessarily make a better beer, but rather gives the beer more clarity and typically preserves more beer flavor than heated pasteurization. The time from brewing to having the finished beer is also shortened, thereby boosting productivity. Unfortunately, cold filtering is a touchy process and over filtering can remove components that contribute to the color, flavor, body, and head of the beer.

The definition of pasteurization is simply heating beer to destroy microbes. More specifically in the process of pasteurization the beer is heated up, but only for a few seconds, which is long enough to kill any yeast or bacteria that could change the flavor of the beer.

Most mainstream beers are either cold filtered to remove the yeast and bacteria, or heat pasteurized to kill all yeast and bacteria, so the result of both processes is the same, insuring that there are no organisms left over that could change the flavor of the beer or the finished product. Both generally result in a clear beer.

So if they both do virtually the same thing which one is better to use? Due to the higher cost of conducting heat pasteurization and the more altered beer flavor it tends to produce, most would argue that cold filtering the beer is the better option. The lower cost, clearness of the beer, and less altered flavor that comes from cold filtration recaps again why it is the more superior filtering method.

So, we know both of these produce clear beers, but what is the haze you see in other beers? Any particles that remain suspended in a beer leaving the final product less clear than anticipated is what we refer to as haze. A bulk of beer hazes are caused by proteins and tannins; and the haze begins to appear as these components join together and become big enough to see with the naked eye.

Beer haze can come in two forms, a biological haze, which is due to living things, or a non-biological haze, which is due to everything else. Filtration is not your answer to any biological or bacterial contamination, instead this is largely due to poor brewing practices. Non-biological hazes on the other hand get subdivided into two categories: chill haze and permanent haze. If a beer is hazy when chilled to 32 degrees Fahrenheit, but clear when warmed to any temperature above that, your beer is said to have a chill haze, but if a beer is hazy at all temperatures it has a permanent haze.

What filtration system or tools do brewers use to get rid of these hazes found in beer? The filter system used by many brewers is purely mechanical and extremely simple. Brewers construct a screen with holes tiny enough to not permit the passage of unwanted particles, but big enough to allow the liquid to still flow through. Filtering billions of microscopic particles from beer also requires pressure, CO2 pressure to be more specific. The CO2 pressure forces the beer through the filter material, and is a must when it comes to filtering. You may hear some filters being called micron filters, which defines it by the average particle size that can filter through it, with its size listed in microns.

How filtering works is that beer enters an inlet, passes through some filter material, and exits out of an outlet. This process makes filter material an integral part of the filter housing or filter cartridge. Filters used for beer are used exactly the same as filters sold for household drinking water.

Both cold filtering and pasteurizing a beer filters out unwanted parts in one way or another, but there is another form of beer that completely differs, unfiltered beer. Unfiltered beer is the natural state of beer, and remains consistent with what craft beer is and should be. It still contains all the yeast cells and protein polyphenol aggregations that make the beer cloudy.

If you're interested in trying different types of beer, including cold filtered ones, check out our Beer of the Month Club!