Editing Brewing (section)

====Cool fermentation====
{{anchor|Cool fermentation}}{{anchor|Cool fermenting}}
{{Main|Lager}}

When a beer has been brewed using a cool fermentation of around {{convert|10|°C|°F|abbr=on}}, compared to typical warm fermentation temperatures of {{convert|18|°C|°F|abbr=on}},<ref>{{cite book|url=https://books.google.com/books?id=Q82QAwAAQBAJ&pg=PT114|page=94|title=Yeast: The Practical Guide to Beer Fermentation|author=Chris White, Jamil Zainasheff|publisher=Brewers Publications|date=1 February 2010|isbn=9781938469060|archive-url=https://web.archive.org/web/20191222170637/https://books.google.com/books?id=Q82QAwAAQBAJ&pg=PT114|archive-date=22 December 2019|url-status=live}}</ref><ref>{{cite book|url=https://archive.org/details/palealehistorybr0000fost|url-access=registration|page=[https://archive.org/details/palealehistorybr0000fost/page/185 185]|title=Pale Ale|author=Terry Foster|publisher=Brewers Publications|date=7 April 1999|isbn=9781938469251}}</ref> then stored (or lagered) for typically several weeks (or months) at temperatures close to [[freezing]] point, it is termed a "[[lager]]".<ref>{{cite book|url=https://books.google.com/books?id=Ga4MYyZq-RMC&pg=PA533|page=533|author=Garrett Oliver|title=The Oxford Companion to Beer|publisher=Oxford University Press|date=2011|isbn=9780195367133|author-link=Garrett Oliver|access-date=19 November 2015|archive-url=https://web.archive.org/web/20160528215325/https://books.google.com/books?id=Ga4MYyZq-RMC&pg=PA533|archive-date=28 May 2016|url-status=live}}</ref> During the lagering or storage phase several flavour components developed during fermentation dissipate, resulting in a "cleaner" flavour.<ref>{{cite book|url=https://books.google.com/books?id=pkzx2TeYYT8C&pg=RA1-PA970|page=970|title=Comprehensive Natural Products II: Chemistry and Biology|author=Craig Townsend|publisher=Elsevier|date=2010|isbn=9780080453828|archive-url=https://web.archive.org/web/20191221030510/https://books.google.com/books?id=pkzx2TeYYT8C&pg=RA1-PA970|archive-date=21 December 2019|url-status=live}}</ref><ref>{{cite book|url=https://books.google.com/books?id=Ga4MYyZq-RMC&pg=PA532|page=532|author=Garrett Oliver|title=The Oxford Companion to Beer|publisher=Oxford University Press|date=2011|isbn=9780195367133|author-link=Garrett Oliver|access-date=30 August 2017|archive-url=https://web.archive.org/web/20191219235900/https://books.google.com/books?id=Ga4MYyZq-RMC&pg=PA532|archive-date=19 December 2019|url-status=live}}</ref> Though it is the slow, cool fermentation and cold conditioning (or lagering) that defines the character of lager,<ref>{{cite book|url=https://books.google.com/books?id=CazaCgAAQBAJ&pg=PR21|page=xxi|title=New Brewing Lager Beer|author=Gregory J. Noonan|publisher=Brewers Publications|date=17 September 2003|isbn=9781938469237|archive-url=https://web.archive.org/web/20191222040341/https://books.google.com/books?id=CazaCgAAQBAJ&pg=PR21|archive-date=22 December 2019|url-status=live}}</ref> the main technical difference is with the yeast generally used, which is ''[[Saccharomyces pastorianus]]''.<ref>{{cite book |chapter-url=https://books.google.com/books?id=hBO3N5qLTEIC&pg=PA89|page=89|title=Beer in Health and Disease Prevention |chapter=8 The Brewer's Yeast Genome |author=Sandra Rainieri |publisher=Academic Press |date=28 April 2011 |isbn=9780080920498}}</ref> Technical differences include the ability of lager yeast to metabolize [[melibiose]],<ref name="Boekhout Robert 2003" /> and the tendency to settle at the bottom of the fermenter (though ale yeasts can also become bottom settling by selection);<ref name="Boekhout Robert 2003">{{cite book|url=https://books.google.com/books?id=XqmjAgAAQBAJ&pg=PA349|page=349|title=Yeasts in Food|author=T Boekhout, V Robert|publisher=Elsevier|date=7 May 2003|isbn=9781845698485|archive-url=https://web.archive.org/web/20191223172609/https://books.google.com/books?id=XqmjAgAAQBAJ&pg=PA349|archive-date=23 December 2019|url-status=live}}</ref> though these technical differences are not considered by scientists to be influential in the character or flavour of the finished beer, brewers feel otherwise – sometimes cultivating their own yeast strains which may suit their brewing equipment or for a particular purpose, such as brewing beers with a high abv.<ref>{{cite book |title=Brewing: science and practice |author=Briggs, Dennis Edward |display-authors=et al |publisher=Elsevier |date= 2004|page=123}}</ref><ref>{{cite book|url=https://books.google.com/books?id=f--1V1ftgtsC&pg=PA132|page=132|title=Kirk-Othmer Food and Feed Technology: Volume 1|publisher=John Wiley & Sons|date=2007|isbn=9780470174487|archive-url=https://web.archive.org/web/20191222163820/https://books.google.com/books?id=f--1V1ftgtsC&pg=PA132|archive-date=22 December 2019|url-status=live}}</ref><ref>{{cite web|url=https://www.businessinbrighton.org.uk/blog/2013/11/08/harveys-let-us-some-brewing-secrets|title=Harveys let us in on some brewing secrets|work=businessinbrighton.org.uk|author=Dan Rose|access-date=27 January 2017|archive-url=https://web.archive.org/web/20170202061613/https://www.businessinbrighton.org.uk/blog/2013/11/08/harveys-let-us-some-brewing-secrets|archive-date=2 February 2017|url-status=live}}</ref><ref>{{cite book|url=https://books.google.com/books?id=Ga4MYyZq-RMC&pg=PA331|page=331|author=Chris White|title=The Oxford Companion to Beer|publisher=Oxford University Press|date=9 September 2011|isbn=9780195367133|archive-url=https://web.archive.org/web/20191228080342/https://books.google.com/books?id=Ga4MYyZq-RMC&pg=PA331|archive-date=28 December 2019|url-status=live}}</ref>
[[File:Timmermans.jpg|thumb|200px|Spontaneous fermentation at [[Timmermans Brewery|Timmermans]] in Belgium]]
Brewers in [[Bavaria]] had for centuries been selecting cold-fermenting yeasts by storing ("lagern") their beers in cold alpine caves. The process of natural selection meant that the wild yeasts that were most cold tolerant would be the ones that would remain actively fermenting 
in the beer that was stored in the caves. A sample of these Bavarian yeasts was sent from the Spaten brewery in Munich to the Carlsberg brewery in Copenhagen in 1845 who began brewing with it. In 1883 Emile Hansen completed a study on pure yeast culture isolation and the pure strain obtained from Spaten went into industrial production in 1884 as Carlsberg yeast No 1. Another specialized pure yeast production plant was installed at the Heineken Brewery in Rotterdam the following year and together they began the supply of pure cultured yeast to brewers across Europe.<ref>Meussdoerffer, Franz G. "A comprehensive history of beer brewing". ''Handbook of brewing: processes, technology, markets'' (2009): 1–42.</ref><ref>Boulton, Christopher, and David Quain. ''Brewing yeast and fermentation''. John Wiley & Sons, 2008.</ref> This yeast strain was originally classified as ''Saccharomyces carlsbergensis'', a now defunct species name which has been superseded by the currently accepted taxonomic classification ''Saccharomyces pastorianus''.<ref>{{cite book|url=https://books.google.com/books?id=Y4RgCgAAQBAJ&pg=PA428|page=428|title=Advances in Bioprocess Technology|author=Pogaku Ravindra|publisher=Springer|date=13 August 2015|isbn=9783319179155|archive-url=https://web.archive.org/web/20191221202844/https://books.google.com/books?id=Y4RgCgAAQBAJ&pg=PA428|archive-date=21 December 2019|url-status=live}}</ref>