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English Views: 24 Author: Site Editor Publish Time: 2025-07-24 Origin: Site
Filtration is the process of passing a liquid through a porous medium to remove solids. The effectiveness of filtration depends on the particle size and porosity of the filter medium. There are two basic types of filtration: depth filtration and surface filtration.
Depth filtration, also known as powder filtration, uses complex channels in the filter medium to capture particles. The medium can be diatomaceous earth (DE), perlite, or other porous media. Depth filtration is often considered coarse or primary filtration, but in many small breweries it is the only filtration performed.
Surface filtration uses a membrane material with a pore size smaller than the particles to be removed. As the clarified liquid flows through, the particles are retained on the filter surface. If the pore size is a certain size (e.g., up to 5 μm), the filtration is said to be "absolute" based on pore size. Membrane filtration and cross-flow filtration are examples.
Any particulate matter suspended in beer that makes the beer less transparent than expected can be called haze. There are two main types of beer haze: haze caused by living organisms (biological), and haze caused by other substances (abiotic). Most brewers probably want to distinguish between haze caused by bacterial or wild yeast contamination, and haze caused by brewer's yeast.
Successful filtering of beer requires an understanding of the different sized particles present and composition in beer. The goal of filtration is to remove the vast majority of yeast while retaining enough protein to not affect the persistence of the head. While the goal of filtration or clarification is not to remove hops, hops do adhere to yeast cells. Therefore, removing yeast can sometimes result in a reduction in hop flavor.
Yeast cell size is usually in the 5-10 micron range, so coarse or fine filtration is usually done in the 5 micron range. This is the typical size of diatomaceous earth (DE or Kieselguhr) filters commonly used in small breweries. This is also a common size for plate and frame filters using disposable filter pads. In professional breweries, the choice of DE or filter pad depends on the tightness of the filter media.
Beer haze is often viewed as a colloidal stability issue. A colloid is defined as "a suspension of fine particles in a continuous medium...". Colloidal stability refers to the absence of the two main types of haze in the finished beer.
Chill haze: A haze that forms when beer is cooled to 0 degrees Celsius (32 degrees Fahrenheit) and redissolves when the beer is reheated to 20 degrees Celsius (68 degrees Fahrenheit) or higher. Particle size ranges from 0.1 to 1.0 microns.
Permanent haze: A haze that appears when beer is cooled to 20°C or higher. Particle size ranges from 1-10 microns.
Plate and Frame Filters: Consists of vertical plates covered with filter cloth or pads. Next to the plates is a hollow frame filled with filter aids. These filter aids are arranged alternately over the entire length of the filter, ending in end plates.
Mesh Filters: A hollow mesh screen (blades) mounted on a central axis inside a cylindrical container. In a process called "prefiltration", a mixture of beer (or water) and dehydration active ingredients (DE) is pumped into the container and circulated until all the DE is retained by the filter mesh and the liquid becomes clear.
Candle Filters: Candle filters are similar to vertical mesh filters, but instead of blades, they have hollow cylindrical tubes with slit openings. They operate in the same way, but candle filters have a larger surface area, filter faster, and use less filter aids.
Membrane Filters: Membrane filters are made of polymer materials that capture particles through their uniform pore size. They produce very good filtration of liquids, but sometimes they become clogged.
Cross-flow filtration: Cross-flow filtration improves on conventional membrane filtration by pumping liquid across a filter surface (usually sintered alumina). Deposited solids are captured and drained away, preventing clogging of the filter surface. These filters are generally well designed but are expensive to purchase and operate.
Beer filtration is essential to stabilize the quality of beer and extend its shelf life. Unfiltered beer contains residual yeast and other microorganisms that will continue to ferment, causing the beer to have off-flavors, cloudiness, and may even burst from overcarbonation. Filtration removes these undesirable substances and prevents the beer from further fermentation, ensuring that the beer remains stable for a long time.
The quality of filtration affects the flavor of the beer. Filtration removes unwanted particles and helps reduce potential off-flavors caused by yeast, bacteria, or protein mist. Filtration also helps improve the smooth taste of the beer, ensuring that the beer tastes clean and fully reflects the subtle differences of the ingredients. The quality of the beer can be achieved by achieving batch-to-batch flavor consistency.
Beer filtration is an important quality control measure for breweries. It removes any visible and invisible impurities that may affect the taste, aroma, and stability of the beer. By implementing a rigorous filtration process, brewers can ensure that every pint of beer meets their high standards and provides consumers with a high-quality product. This quality control is essential to earning the trust of beer lovers who seek unparalleled enjoyment with every sip of beer.
