Chapter 15

Beer Filtration

(book excerpts)

After conditioning, clarification and stabilization the beer is filtered to remove any remaining yeast and the removal of precipitated protein and polyphenol haze material. The key role of filtration in beer brewing is to provide stabilization. Physical-chemical stabilization prevents the formation of hazes and deposits after packaging, while microbiological stabilization eliminates yeasts and bacteria that can destroy a beer’s taste. Filtration is carried out at low temperature (possibly at -2 to -1 degrees C, 28–30°F) under a counterpressure of carbon dioxide above its saturation level. Many types of filtration systems are available to the brewer, each with its own advantages or disadvantages, and these can include pressure leaf filters, plate and frame filters, lenticular disc filters, membrane filters, and tangential flow (cross-flow) filters. These systems use different filter media including diatomaceous earth, cellulose pads, lenticular discs, membranes with calibrated pores, and tangential filtration through inorganic or organic membranes. Important characteristics of filtration media are the porosity, which is the percentage of empty space in a porous structure in relation to total volume, and their permeability, which represents the ability of a medium to transmit fluids through at more or less at high rates. Depending on the initial state of the beer clarity (quantity and type of solids in suspension) the beer may undergo a series of filtration steps—rough, polish, and sterile. In all cases it is essential to exclude oxygen to prevent adverse staling effects.

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