Editing Yeast (section)

===={{anchor|Beer}}Beer ====
{{Main|Brewing}}
{{see also|Barm}}
[[File:NM.0019545 Jästkrans.jpg|thumb|[[Yeast ring]] used by Swedish farmhouse brewers in the 19th century to preserve yeast between brewing sessions.]]<!-- This section is linked from [[Swedish beer]], [[Brewer's yeast]], [[Brewers yeast]], [[Brewing yeast]], [[Brewing Yeast]], [[Brewer's Yeast]], and [[Brewers' yeast]] -->
[[File:2009-03-21 Beer brewing bubbles.jpg|right|thumb|Bubbles of [[carbon dioxide]] forming during beer-brewing<ref name="Ostergaard-2000"/>]]
Brewing yeasts may be classed as "top-cropping" (or "top-fermenting") and "bottom-cropping" (or "bottom-fermenting").<ref>{{cite book|vauthors=Priest FG, Stewart GG |date=2006 |url=https://books.google.com/books?id=TIYbNdrIsPEC&pg=PA84 |page=84 |publisher=CRC Press |title=Handbook of Brewing|isbn=9781420015171 }}</ref> Top-cropping yeasts are so called because they form a foam at the top of the [[wort]] during fermentation. An example of a top-cropping yeast is ''[[Saccharomyces cerevisiae]]'', sometimes called an "ale yeast".<ref name="Gibson-2010"/> Bottom-cropping yeasts are typically used to produce [[lager]]-type beers, though they can also produce [[ale]]-type beers. These yeasts ferment well at low temperatures. An example of bottom-cropping yeast is ''[[Saccharomyces pastorianus]]'', formerly known as ''S.&nbsp;carlsbergensis''.

Decades ago,{{vague|date=March 2018}} taxonomists reclassified ''S.&nbsp;carlsbergensis'' (uvarum) as a member of ''S.&nbsp;cerevisiae'', noting that the only distinct difference between the two is metabolic. {{dubious |reason=In conflict with newer sources cited by “Saccharomyces uvarum” article. Could be a lumper/splitter thing, but the names ain’t invalid yet.|date=January 2022}} Lager strains of ''S.&nbsp;cerevisiae'' secrete an enzyme called melibiase, allowing them to hydrolyse [[melibiose]], a [[disaccharide]], into more fermentable [[monosaccharide]]s. Top- and bottom-cropping and cold- and warm-fermenting distinctions are largely generalizations used by laypersons to communicate to the general public.<ref>For more on the taxonomical differences, see {{cite book |author=Dowhanick TM |chapter=Yeast&nbsp;– Strains and Handling Techniques |title=The Practical Brewer |editor=McCabe JT |publisher=Master Brewers Association of the Americas |year=1999}}</ref>

The most common top-cropping brewer's yeast, ''S.&nbsp;cerevisiae'', is the same species as the common baking yeast.<ref name="Amendola-2002"/> Brewer's yeast is also very rich in [[essential mineral]]s and the [[B vitamin]]s (except B<sub>12</sub>), a feature exploited in food products made from leftover ([[by-product]]) yeast from brewing.<ref name="University of Maryland Medical Center"/> However, baking and brewing yeasts typically belong to different strains, cultivated to favour different characteristics: baking yeast strains are more aggressive, to carbonate [[dough]] in the shortest amount of time possible; brewing yeast strains act more slowly but tend to produce fewer off-flavours and tolerate higher alcohol concentrations (with some strains, up to 22%).

''[[Dekkera/Brettanomyces]]'' is a genus of yeast known for its important role in the production of '[[lambic]]' and specialty [[sour ale]]s, along with the secondary conditioning of a particular Belgian [[Trappist beer]].<ref name="Vanderhaegen-2003"/> The taxonomy of the genus ''Brettanomyces'' has been debated since its early discovery and has seen many reclassifications over the years. Early classification was based on a few species that reproduced asexually (anamorph form) through multipolar budding.<ref name="Custers-1940"/> Shortly after, the formation of ascospores was observed and the genus ''Dekkera'', which reproduces sexually (teleomorph form), was introduced as part of the taxonomy.<ref name="VanderWalt-1984"/> The current taxonomy includes five species within the genera of ''Dekkera/Brettanomyces''. Those are the anamorphs ''[[Brettanomyces bruxellensis]]'', ''[[Brettanomyces anomalus]]'', ''[[Brettanomyces custersianus]]'', ''[[Brettanomyces naardenensis]]'', and ''[[Brettanomyces nanus]]'', with teleomorphs existing for the first two species, ''[[Dekkera bruxellensis]]'' and ''[[Dekkera anomala]]''.<ref name="Oelofse-2008"/> The distinction between ''Dekkera'' and ''Brettanomyces'' is arguable, with Oelofse et al. (2008) citing Loureiro and Malfeito-Ferreira from 2006 when they affirmed that current molecular DNA detection techniques have uncovered no variance between the anamorph and teleomorph states. Over the past decade, ''Brettanomyces'' spp. have seen an increasing use in the craft-brewing sector of the industry, with a handful of breweries having produced beers that were primarily fermented with pure cultures of ''Brettanomyces'' spp. This has occurred out of experimentation, as very little information exists regarding pure culture fermentative capabilities and the aromatic compounds produced by various strains. ''Dekkera''/''Brettanomyces'' spp. have been the subjects of numerous studies conducted over the past century, although a majority of the recent research has focused on enhancing the knowledge of the wine industry. Recent research on eight ''Brettanomyces'' strains available in the brewing industry focused on strain-specific fermentations and identified the major compounds produced during pure culture anaerobic fermentation in wort.<ref name="Yakobson-2010"/>