Yeast extract

Viscous yeast extract

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, an amino acid found in meat, cheese, fungi and vegetables, including mushrooms, broccoli, and tomatoes.^[1] According to Joe Dickson, a past member of the USDA's National Organic Standards Board,^[2] A number of consumer groups have claimed that certain food ingredients, such as autolyzed yeast and hydrolyzed protein, are MSG in disguise. Large food retailers dispute this.^[3]

Autolyzed yeast

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).

Marmite yeast extract

Yeast autolysates are used in AussieMite, Mightymite, Vegemite (Australia), Marmite, Promite, Oxo (Ireland, New Zealand, Canada, 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

Hydrolyzed yeast or hydrolyzed yeast extract is another version used as a flavour enhancer. Exogenous enzymes or acids are used to hydrolyze the proteins. It mimics MSG when combined with sodium.

References

• Herbst, Sharon (2001). Food Lover's Companion. Hauppauge, New York: Barron's Educational Series, Inc. 

External links

• yeastextract.info: Homepage of Eurasyp (European Association of Specialty Yeast Products)