How Beer Filtration Works

What is beer filtration?

After conditioning, clarifying, and stabilizing, beer undergoes filtration to remove residual yeast, precipitated proteins, and hazy polyphenols. Filtration plays a key role in the brewing process by ensuring beer stability. Physicochemical stabilization prevents haze and sedimentation after packaging, while microbiological stabilization eliminates yeast and bacteria that can damage the beer's flavor. Filtration is performed at low temperatures (typically -2 to -1 degrees Celsius, 28-30°F) with a CO2 backpressure above saturation levels. Filtration can be performed at different stages of the brewing process, depending on the desired outcome and the type of beer being produced.

Filtration targets various compounds and particles in beer, including:

• Yeast cells: Yeast is essential for fermentation, but if left in the finished product, it can cause off-flavors or a cloudy appearance.

• Proteins and polyphenols: These compounds contribute to haze and may also result in an unpleasant taste or texture.

• Microbiological: Filtration can help remove bacteria and other microorganisms that can damage the beer or cause off-flavors.

• Other particles: Filtration can also remove larger particles, such as hop fragments, grain particles, or other sediment.

Beer Filtration Process

• Post-fermentation Preparation: After fermentation, beer typically undergoes preliminary treatments such as cooling and settling. This stage allows solid particles, such as yeast and grain residue, to settle to the bottom of the liquid, making subsequent filtration more effective.

• Primary Filtration: Primary Filtration is the first filtration step in the beer brewing process, primarily removing larger solid particles and suspended matter through physical methods.

• Secondary Filtration: Secondary Filtration is a filtration step designed to further improve the clarity and stability of the beer. During this stage, finer filters or media are used to remove smaller solid particles and microorganisms, such as residual yeast cells and fine suspended matter.

• Cold Filtration: Cold Filtration may be performed for beers requiring exceptional clarity, such as pale ales or some premium craft beers. This step further removes fine suspended matter and undissolved solids, resulting in a beer with even higher clarity and flavor.

Types of Beer Filtration

Depth Filtration

Depth filtration involves introducing a medium into the beer that binds to large particles suspended in the beer, typically yeast and proteins, but also often polyphenols and esters. Diatomaceous earth and perlite are the two most commonly used binders for depth filtration. These media are in powder form and must be handled with care. Brewers must wear protective gear, including masks, as these agents can be inhaled and bind to particles in the lungs and other organs. These agents are often expensive.

Surface Filtration

Mesh screens are a modern version of cheesecloth and come in a variety of sizes, from large filters 5 microns and above to smaller filters 0.5 microns and below. Large filters capture larger particles but retain yeast and other tannins that are essential to the beer; small filters can capture even yeast and other small particles but can also remove flavor and aroma.

Single-Filtered and Double-Filtered Beer

Some brewers even filter their beer three times to achieve the purest beer. This process may include deep filtration and two rounds of surface filtration. Many mass-produced beers are triple-filtered.

Filtration Systems

Most surface filters are in-line cartridge filters, which can be removed and replaced when the filter screen becomes clogged. You can also change the filter size as needed. Most craft brewers recommend starting with a larger filter and avoid using the smallest filter with a pore size smaller than 0.5 microns, as this removes the essence of the beer.

What equipment is available for beer filtration?

Plate beer filters

This is a simple filtration device used for primary and secondary filtration of beer. It uses cellulose plates of varying porosity as the filter material. The beer is filtered through multiple cycles—first through a coarse-pore plate, then through a fine-pore plate. The disadvantage of this type of filter is the time-consuming cleaning and disinfection required after each filtration. Its advantage is its low purchase price. Plate filters are recommended for small, start-up craft breweries.

Diatomaceous earth beer filters

Candle-type beer filters with diatomaceous earth are the most commonly used equipment for primary to fine filtration of beer. The filter material is diatomaceous earth, a finely ground mixture of prehistoric algae shells—learn more about diatomaceous earth. The diatomaceous earth is applied to the stainless steel candle filter by controlling the flow rate of beer through the filter. The advantage of diatomaceous earth filters is that they are very easy and quick to clean and disinfect after filtration. If the diatomaceous earth layer becomes clogged with impurities, it can be easily and quickly rinsed away, allowing for the next filtration cycle to begin immediately. Diatomaceous earth with varying porosity can be used for beer filtration, from coarse to medium to fine filtration.

Beer Microfiltration Stations

Microfiltration stations are used to ultra-finely filter beer before it is bottled, kegged, canned, or canned. The beer is filtered through a very fine membrane mounted on a replaceable stainless steel candlestick. Through the appropriate selection and combination of microfiltration elements, complete microbiological and colloidal stability of the beer can be achieved, resulting in a very long drinking life, which is crucial for distributing beer to retail outlets, particularly in bottles and cans. Beer microfiltration completely replaces pasteurization without unnecessary heating of the beverage. This results in a beer with a better taste and other sensory properties than pasteurization.

Membrane Filters

Membrane filters are a new type of beer filtration equipment that uses a microporous membrane as the filtration medium. They offer advantages such as high filtration accuracy and high filtration speed, but they are expensive and require regular cleaning and replacement of the membrane.

Filtration Process for Homebrewers

Basic Filtration Options

For those just starting homebrewing or on a tight budget, there are several cost-effective and user-friendly beer filtration options.

• Funnel with Fine Mesh Filter: This is one of the simplest and most economical ways to filter beer. Placing a fine mesh filter over the funnel effectively removes larger particles, such as hop residue and some yeast cells, resulting in a clearer beer.

• Filter Bag: Filter bags, typically made of nylon or polyester, can be used to filter beer during the transfer process. This method is convenient and helps remove larger particles from the beer.

• Plate Filter System: This system utilizes a filter plate between two plates to filter beer. While the plate filter system requires a slightly higher investment than the previously mentioned options, it offers higher filtration efficiency and is suitable for small-scale homebrewing.

Advanced Filtration Options

More experienced homebrewers or those seeking a clearer finished product may opt for more advanced filtration methods.

• Cartridge Filters: These filters come in a variety of pore sizes to suit different brewing needs and offer higher filtration efficiency than standard filters. Cartridge filters are typically housed in a filter housing and can be used with a pump to enhance filtration efficiency. This setup allows for greater control over flow rate and pressure, ensuring optimal results.

• Small Commercial Filtration Systems: Some homebrewers may choose to invest in a small commercial filtration system, such as a cross-flow filter or depth filter, to achieve professional-grade clarity in their finished beer. While these systems are more expensive and require a larger initial investment, they offer superior filtration performance.

Filtration Accessories

In addition to the primary filtration methods, homebrewers can also purchase a variety of accessories to enhance the filtration process.

• Inline Filters: These filters can be added to the transfer line during kegging to capture any remaining particles and further enhance the clarity of the finished beer.

• Oxygenation Systems: Proper oxygenation during the transfer process is crucial for yeast health and helps prevent oxidation. Some homebrewers choose to use an inline oxygenation system, introducing oxygen as the beer is being filtered, ensuring the yeast has the necessary resources for a healthy fermentation.