Yeast extract
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explained glutamic acid formation
'''Yeast extract''' is the common name for various forms of processed [[yeast]] products that are used as food additives or flavourings. They are often used in the same way that [[monosodium glutamate]] (MSG) is used, and, like MSG, often contain free [[glutamic acid]]s. The texture ranges from liquid to a light paste. (Herbst p.681) Glutamic acid in yeast extracts are produced from an acid-base fermentation cycle, only found in some yeasts, typically ones bred for use in baking.
==Autolyzed yeast==
'''[[Autolysis (biology)|Autolyzed]] yeast''' or '''autolyzed yeast extract''' consists of concentrations of [[yeast]] cells that are allowed to die and break up, so that the yeasts' [[digestion|digestive]] enzymes break their [[protein]]s down into simpler compounds.
Yeast autolysates are used in [[Vegemite]] ([[Australia]]), [[Marmite]], [[Promite]], [[Oxo (food)|Oxo]] ([[New Zealand]], [[South Africa]], [[United Kingdom]], and [[Republic of Ireland]]), and [[Cenovis]] ([[Switzerland]]). [[Bovril]] (The [[United Kingdom]] and [[Republic of Ireland]]) switched from beef extract to yeast extract for 2005 and most of 2006, but later switched back. Autolyzed yeast extract is also the primary source of [[monosodium glutamate]] for the food industry.{{Fact|date=April 2007}} <!-- this statement is either wrong or poorly qualified -->
==Hydrolyzed yeast==
'''[[Hydrolysis|Hydrolyzed]] yeast''' or '''hydrolyzed yeast extract''' is another widely used food additive, used for flavouring purposes.
==Manufacture==
The general method for making yeast extract for food products such as [[Vegemite]] and [[Marmite]] on a commercial scale is to add salt to a suspension of yeast making the solution hypertonic, which leads to the cells shrivelling up; this triggers [[autolysis]], in which the yeast self-destructs. The dying yeast cells are then heated to complete their breakdown, after which the husks (yeast with thick cell walls which wouldn't do the texture much good) are separated.
==See also==
*[[Starch]]
[[Category:Food ingredients]]
[[Category:Microbiological media ingredients]]
[[Category:Yeast extract spreads|*]]
[[Category:Umami enhancers]]
==Sources==
*{{cite book
| last = Herbst
| first = Sharon
| authorlink = Sharon Herbst
| coauthors =
| title = Food Lover's Companion
| publisher = [[Barron's Educational Series, Inc.]]
| date = [[2001]]
| location = [[Hauppauge, New York]]
| pages =
| url =
| id = }}
[[de:Hefeextrakt]]
[[es:Extracto de levadura]]
[[ja:酵母エキス]]
[[uk:Екстракт дріжджів]]