Brewing

Brewing is the production of beer by steeping a starch source (commonly cereal grains, the most popular of which is barley)^[1] in water and fermenting the resulting sweet liquid with yeast. It may be done in a brewery by a commercial brewer, at home by a homebrewer, or communally.^[2] Brewing has taken place since around the 6th millennium BC, and archaeological evidence suggests that emerging civilizations, including ancient Egypt,^[3] China,^[4] and Mesopotamia, brewed beer.^[5] Since the nineteenth century the brewing industry has been part of most western economies.

The basic ingredients of beer are water and a fermentable starch source such as malted barley. Most beer is fermented with a brewer's yeast and flavoured with hops.^[6] Less widely used starch sources include millet, sorghum and cassava.^[7] Secondary sources (adjuncts), such as maize (corn), rice, or sugar, may also be used, sometimes to reduce cost, or to add a feature, such as adding wheat to aid in retaining the foamy head of the beer.^[8] The most common starch source is ground cereal or "grist" - the proportion of the starch or cereal ingredients in a beer recipe may be called grist, grain bill, or simply mash ingredients.^[9]

Steps in the brewing process include malting, milling, mashing, lautering, boiling, fermenting, conditioning, filtering, and packaging. There are three main fermentation methods: warm, cool and spontaneous. Fermentation may take place in an open or closed fermenting vessel; a secondary fermentation may also occur in the cask or bottle. There are several additional brewing methods, such as Burtonisation, double dropping, and Yorkshire Square, as well as post-fermentation treatment such as filtering, and barrel-ageing.