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Conditioning
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After an initial or primary fermentation, beer is conditioned, matured or aged,[1] in one of several ways,[2] which can take from 2 to 4 weeks, several months, or several years, depending on the brewer's intention for the beer. The beer is usually transferred into a second container, 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 flavours and harmful compounds such as acetylaldehyde.[3]
- Kräusening
Kräusening is a conditioning method in which fermenting wort is added to the finished beer.[4] The active yeast will restart fermentation in the finished beer, and so introduce fresh carbon dioxide; the conditioning tank will be then sealed so that the carbon dioxide is dissolved into the beer producing a lively "condition" or level of carbonation.[4] The kräusening method may also be used to condition bottled beer.[4]
- Lagering
Lagers are stored at near freezing temperatures for 1–6 months while still on the yeast.[5] The process of storing, or conditioning, or maturing, or aging a beer at a low temperature for a long period is called "lagering", and while it is associated with lagers, the process may also be done with ales, with the same result – that of cleaning up various chemicals, acids and compounds.[6]
- Secondary fermentation
During secondary fermentation, most of the remaining yeast will settle to the bottom of the second fermenter, yielding a less hazy product.[7]
- Bottle fermentation
Some beers undergo a fermentation in the bottle, giving natural carbonation.[8] This may be a second or third fermentation. They are bottled with a viable yeast population in suspension. If there is no residual fermentable sugar left, sugar or wort or both may be added in a process known as priming. The resulting fermentation generates CO2 that is trapped in the bottle, remaining in solution and providing natural carbonation. Bottle-conditioned beers may be either filled unfiltered direct from the fermentation or conditioning tank, or filtered and then reseeded with yeast.[9]
- Cask conditioning
Cask ale or cask-conditioned beer is unfiltered and unpasteurised beer that is conditioned (including secondary fermentation) and served from a cask, either pumped up from a cellar via a beer engine (hand pump), or from a tap by gravity.[10] Sometimes a cask breather is used to keep the beer fresh by allowing carbon dioxide to replace oxygen as the beer is drawn off the cask.[11] The term "real ale" as used by the Campaign for Real Ale (CAMRA) refers to beer "served without the use of extraneous carbon dioxide", which would disallow the use of a cask breather.[12][13]
- ^ F. G. Priest; Graham G. Stewart (22 February 2006). Handbook of Brewing. CRC Press. p. 86. ISBN 9780824726577. Retrieved 16 July 2012.
- ^ Ian Spencer Hornsey (25 November 1999). Brewing. Royal Society of Chemistry. p. 141. ISBN 9780854045686. Retrieved 16 July 2012.
- ^ F. G. Priest; Graham G. Stewart (22 February 2006). Handbook of Brewing. CRC Press. p. 308. ISBN 9780824726577. Retrieved 16 July 2012.
- ^ a b c Keith Thomas (7 October 2011). The Oxford Companion to Beer. Oxford University Press. ISBN 9780195367133. Retrieved 16 July 2012.
- ^ Briggs, D.E.; Boulton, C.A.; Brookes, P. A.; and Stevens, R. Brewing, 2004, CRC. ISBN 0-8493-2547-1 p. 5.
- ^ Horst Dornbusch (9 September 2011). "Lagering". The Oxford Companion to Beer. Oxford University Press. pp. 533–534. ISBN 9780195367133. Retrieved 8 April 2013.
- ^ Priest & Stewart 2006, p. 532
- ^ Christopher M. Boulton (20 May 2013). Encyclopaedia of Brewing. Wiley. p. 79. Retrieved 14 June 2013.
- ^ Christopher M. Boulton (20 May 2013). Encyclopaedia of Brewing. Wiley. p. 80. Retrieved 14 June 2013.
- ^ Ian Spencer Hornsey (1 January 1999). Brewing. Royal Society of Chemistry. pp. 150–151.
- ^ Encyclopaedia of Brewing. John Wiley & Sons. 20 May 2013. p. 150.
- ^ "What is Real Ale?". camra.org.uk. Retrieved 13 March 2014.
- ^ Pete Brown (11 August 2011). Man Walks into a Pub. Pan Macmillan. p. 299.