Yeast extract is the common name for various forms of processed yeast products made by extracting the cell contents (removing the cell walls); they are used as food additives or flavourings, or as nutrients for bacterial culture media. They are often used to create savoury flavours and umami taste sensations, and can be found in a large variety of packaged food including frozen meals, crackers, snack foods, gravy, stock and more. Yeast extracts in liquid form can be dried to a light paste or a dry powder.
Yeast extracts and fermented foods contain glutamic acid, which, in solution with sodium ions, is the same as monosodium glutamate. With various controversies that suggest that MSG, an exitotoxin, may be harmful to human health, food manufacturers use yeast extract to avoid adding 'MSG' to the food packaging label.
Autolyzed yeast (containing the cell walls) or autolyzed yeast extract consists of concentrations of yeast cells that are allowed to die and break up, so that the yeasts’ endogenous digestive enzymes break their proteins down into simpler compounds (amino acids and peptides).
Yeast autolysates are used in Vegemite (Australia), Marmite, Promite, Oxo (Ireland, New Zealand, South Africa and the United Kingdom), Cenovis (Switzerland), Vitam-R (Germany) and Maggi sauce. Bovril (Ireland and the United Kingdom) switched from beef extract to yeast extract for 2005 and most of 2006, but later switched back.
The general method for making yeast extract for food products such as Vegemite and Marmite on a commercial scale is to add sodium chloride (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) are separated. Removing the cell walls concentrates the flavours and changes the texture.
Yeast extract is used as a flavour enhancer in processed foods of all kinds.
Hydrolyzed yeast or hydrolyzed yeast extract is another version used as a flavour enhancer. Exogenous enzymes or acids are used to hydrolyze the proteins.
||This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. (June 2012)|
- "Questions and Answers on Monosodium glutamate (MSG)". Retrieved 2014-03-27.
- Herbst, Sharon (2001). Food Lover's Companion. Hauppauge, New York: Barron's Educational Series, Inc.
- yeastextract.info: Homepage of Eurasyp (European Association of Specialty Yeast Products)