Yeast extract:characteristics,production,use

Yeast extract is made from natural bakers’ or brewers’ yeast. Fresh yeast was already an important part of food culture in earlier advanced civilisations. It was not only used for baking bread but also for making beer and wine.

Physiological characteristics

Yeast extract is obtained from fresh yeast in a 5-step process. Enzymes break down the proteins present in the yeast cells into smaller components and dissolve the surrounding cell wall so that the contents leave the cell. The remains of the cell wall are removed by separation. Yeast extract therefore consists of proteins, amino acids, carbohydrates, vitamins and minerals from the yeast cell without the surrounding cell wall.

Production

Yeast extracts in general are produced in three steps: fermentation (growing the yeast), disruption (breaking of the cells), and separation (to keep the soluble part). Although the vast majority of yeast extract spreads are made using von Liebig's traditional approach of heat-autolysis using surplus yeast from beer brewing, other methods do exist for producing specialized types.

In terms of fermentation, spent beer yeast is commonly contaminated with the bitter compounds from hops, requiring a "debittering" step to wash out most of this undesired flavor. Yeast from other sources are not affected by this issue.Spent brewer's yeast is also quite biodiverse, containing yeasts other than traditional Saccharomyces cerevisiae and sometimes beer spoilage-causing lactic acid bacteria too.

For disruption of the cell, some physical and chemical methods may be used in place of the heat-autolysis process. Doing so may allow specific compounds to be extracted or to produce an extract without the hydrolysis of cell contents (as in autolysis) happening.

Use in food

Yeast autolysates are the main ingredient in AussieMite, Mightymite, Vegemite, Marmite, New Zealand Marmite, Promite, Cenovis, Vitam-R, Brazilian Cenovit 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.

Yeast extract is used as a flavoring in foods. It is a common ingredient in American barbecue-flavored potato chips such as Lay's.It is also widely used in soup bases.

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