EnglishViews: 26 Author: Site Editor Publish Time: 2025-07-25 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 clarified liquid flows through, the particles are trapped on the filter surface. If the pore size reaches a certain value (for example, up to 5 μm), the filtration is called "absolute" filtration based on the pore size. Examples are membrane filtration and cross-flow filtration.
Any suspended particles in beer that make the beer less clear than desired can be called hazy. There are two main types of beer haze: haze caused by 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 filtration of beer requires an understanding of the different sizes of particles in beer and their composition. The goal of filtration is to remove most of the yeast while retaining enough protein to not affect the durability of the foam. Although the purpose 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 performed 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 sealing of the filter media.
Beer haze is often viewed as a colloidal stability problem. The definition of a colloid is "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 forms 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 along the entire length of the filter, ending in end plates.
Mesh Filters: Hollow mesh screens (blades) mounted on a central axis inside a cylindrical container. In a process called "prefiltration," a mixture of beer (or water) and dehydrated active ingredient (DE) is pumped into the container and circulated until all the DE is retained by the screens and the liquid becomes clear.
Candle Filters: Candle filters are similar to vertical mesh filters, but use hollow cylindrical tubes with slit openings instead of blades. They work on the same principle, 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 filter liquids very well, but sometimes become clogged.
Cross-Flow Filtration: Cross-Flow Filtration improves on traditional membrane filtration by pumping liquid over the surface of the filter, usually sintered alumina. The deposited solids are captured and discharged, thus preventing the filter surface from clogging. These filters are usually well designed but are expensive to purchase and operate.
