Conditioning, Clarification, Stabilization(book excerpts)
Following primary fermentation, the “green beer” or immature beer undergoes conditioning, also referred to as maturation and aging, in which the green beer is converted into mature beer. The beer is far from finished because it contains suspended particles, lacks sufficient carbonation, lacks taste and aroma, and it is physically and microbiologically unstable. Conditioning is required to convert these off-flavors into those desired by the brewer and to allow the beer to mature and settle into a more stable flavor profile. The beer is usually transferred into a second container (i.e., bright beer tank), but not always, so that it is no longer exposed to the dead yeast and other debris (also known as “trub”) that have settled to the bottom of the primary fermenter. This prevents the formation of unwanted flavors and harmful compounds such as vicinal diketones (VDKs, such as buttery-tasting diacetyl and honey-like pentanedione), hydrogen sulfide (rotten eggs), and acetaldehyde (green apples). After conditioning, clarification is required to remove any remaining yeast and suspended particles formed during conditioning. Cold stabilization refers to protecting the finished product from changes that may occur after packaging. These changes are: (1) flavor changes primarily due to oxidation, (2) nonmicrobiological haze caused by the formation of molecular complexes, and (3) haze produced by the growth of bacteria or yeast.
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