In the process of

brewing Brewing is the production of beer by steeping a starch source (commonly cereal grains, the most popular of which is barley) in water and fermenting the resulting sweet liquid with yeast. It may be done in a brewery by a commercial brewer ...

beer, trub is the term used for the material, along with hop debris, left in the whirlpool or

hopback Brewing is the production of beer by steeping a starch source (commonly cereal grains, the most popular of which is barley) in water and fermenting the resulting sweet liquid with yeast. It may be done in a brewery by a commercial brewer, ...

after the

wort Wort () is the liquid extracted from the mashing process during the brewing of beer or whisky. Wort contains the sugars, the most important being maltose and maltotriose, that will be fermented by the brewing yeast to produce alcohol. Wort als ...

has been boiled then transferred and cooled. Brewers generally prefer that the bulk of the trub be left in the whirlpool rather than stay in contact with the fermenting wort. Although it contains yeast nutrients, its presence can impart

off-flavors Off-flavours or off-flavors ( see spelling differences) are taints in food products caused by the presence of undesirable compounds. They can originate in raw materials, from chemical changes during food processing and storage, and from micro-organ ...

in the finished beer. Trub may also refer to the lees, or layer of sediment, left at the bottom of the fermenter after the

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constit ...

has completed the bulk of the

fermentation Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food p ...

. It is composed mainly of heavy fats, coagulated proteins, and (when in fermenter) inactive yeast. The term has its origins in the German word ''trübe'' (also ''trüb''), which means ''cloudy'', via the brewing and winemaking terms ''Trubstoff'' (''cloudy'' + ''material'') and ''Weintrub'' (''wine'' + ''cloudy'').

References

Brewing {{beer-stub