Brewer's yeast 1452902 214566627 2008-05-24T04:11:13Z Taxman 18034 partial self revert, if it is a brewing byproduct, I don't think it's [[nutritional yeast]] '''Brewer's yeast''' (also known as brewers yeast or brewing yeast) can mean any live [[yeast]] used in [[brewing]]. It can also mean yeast obtained as a by-product of brewing, dried and killed, and used as a [[dietary supplement]] for its [[B vitamin]] content. ==Beer brewing== Beer brewers classify yeasts as [[bottom and top fermenting yeast|top-fermenting and bottom-fermenting]]. This distinction was introduced by the [[Denmark|Dane]] [[Emil Christian Hansen]]. Top-fermenting yeasts (so-called because they float to the top of the beer) can produce higher [[ethanol|alcohol]] concentrations and prefer higher temperatures. An example is ''[[Saccharomyces cerevisiae]]'', known to brewers as [[ale]] yeast. They produce fruitier, sweeter, ale-type beers. Bottom-fermenting yeasts produce fewer of the esters that cause the fruity taste in ale, leaving a crisper taste, and work well at low temperatures. An example of bottom fermenting yeast is ''[[Saccharomyces uvarum]]'', formerly known as ''[[Saccharomyces carlsbergensis]]''. They are used in producing [[lager]]-type beers. Brewers of Bavarian-style [[wheat beer]]s often use varieties of ''[[Torulaspora delbrueckii]]'', which contribute to the distinctive flavour profile. To ensure purity of strain, a 'clean' sample of the [[yeast]] is stored in a laboratory environment at refrigerated temperature. After a certain number of [[Fermentation (food)|fermentation]] cycles, a full scale [[biological reproduction|propagation]] is produced from this laboratory sample. Typically, it is grown up in about three or four stages using sterile Brewing [[wort]] and [[oxygen]]. ==Brettanomyces== {{main|Brettanomyces}} A genus of "wild" yeast used in brewing [[lambic]]. There are three main species: Brettanomyces lambicus; Brettanomyces bruxellensis; and Brettanomyces claussenii, which is found in Britain. ==Dietary supplement== Due to its rapid [[metabolism]], yeast contains a high concentration of the [[B vitamins]], whose functions are related to metabolism, as well as other [[mineral]]s and [[cofactor]]s required for growth. It can therefore serve as a good dietary supplement of these nutrients. "Brewer's yeast" can also refer loosely to any [[nutritional yeast]]. ''S. cerevisiae'' is the usual species for this purpose.<sup>[http://www.diagnose-me.com/treat/T372380.html]</sup> Side effects have not been reported from the use of brewer’s yeast, although allergies to it exist in some people. It is not related to ''Candida albicans'' fungus, which causes yeast infection. Because it contains a highly biologically active form of chromium, supplementation with brewer’s yeast could potentially enhance the effects of drugs for diabetes (e.g., insulin or other blood sugar-lowering agents) and possibly lead to hypoglycemia. Therefore, people with diabetes taking these medications should not supplement with chromium or brewer’s yeast without a doctor's supervision. ''Saccharomyces cerevisiae'' is registered in Europe under the name ''Saccharomyces boulardii'' {{Fact|date=November 2007}}, though the manufacturer states that ''S. boulardii'' is not the same as brewer’s yeast (''S. cerevisiae''). It is marketed as a [[probiotic]] supplement for the treatment of [[diarrhea]] and [[Pseudomembranous colitis|''Clostridium difficile'' colitis]]. There is a case report {{Fact|date=November 2007}} of a person with severely impaired immune function who, after receiving treatment with ''S. boulardii'', developed an invasive fungal infection identified as ''S. cerevisiae''. People with severe impairment of the immune system should therefore not take brewer’s yeast or ''S. boulardii'' unless supervised by a doctor. Use of brewer's yeast as a dietary supplement is thought by some to effectively prevent parasitic insect bites and stings, e.g., mosquitoes. Certain medicines may interact with brewer’s yeast. Refer to drug interactions for a list of those medicines. ==See also== *[[Bottom and top fermenting yeast]] *[[Brettanomyces]] *[[Marmite]] *[[Vegemite]] ==External links== * [http://maltosefalcons.com/tech/MB_Raines_Guide_to_Yeast_Culturing.php Brewing Yeast Propagation and Maintenance: Principles and Practices] *[http://www.whitelabs.com/bacteria.html Brettanomyces by White Labs] [[Category:Brewing]]