Yeast extract

Yeast extract is a concentrate of the soluble ingredients of yeast cells. It is a brown paste or spray dried yellowish-brown, water-soluble powder. Yeast extract contains a high proportion of proteins, amino acids and vitamins of the B group. It does not taste like yeast, but has more of a tangy flavor similar to a meat broth and used as a spread, seasonings and flavor enhancers as well, comparable with nutritional yeast, in health diet. Some of the yeast extract spices or salt may be added.

Production

For the production of yeast extract is taken predominantly protein-rich, specially bred Heferassen ( yeast ), but also brewer's yeast from the brewery, whey and feed yeasts. The disruption of the cells and the associated release of the cell sap is usually by autolysis, ie, the self-dissolution of dead yeast cells. The yeast-inherent proteases and hydrolases then hydrolyze the cell contents, which the proteins into peptides and amino acids, DNA and RNA can be cleaved into nucleotides ( purines and pyrimidines ). To achieve a higher nucleotide content, the yeast-inherent enzymes can be supplemented by the addition of nucleases.

In addition to the autolysis the release of the cell contents can also be done by thermolysis, the yeast cells are heated in water, or by plasmolysis with hypertonic saline or sugar solution. The method can also be combined, such as by autolysis is supported by " melting " of the cell membranes with moderate heat. In principle, also a recovery acid hydrolysis with hydrochloric acid are possible (instead of the enzymatic hydrolysis ), but then the result may not be designated as yeast extract.

The initially liquid car or hydrolyzate is freed in the course from the insoluble cellular components, concentrated, and optionally spray-dried to a dry matter content of 70-80 % for a pasty yeast extract, 95-97 % is achieved with powder.

Composition

Main components of the yeast extract, protein degradation products (peptides, free amino acids ) and DNA degradation products such as purines and pyrimidines.

As an example, the composition of autolytic recovered, spray-dried, salt-free yeast extract with a crude protein content was (this is a summary term for the nitrogen-containing compounds ) of 70 % reproduced. Among the amino acids contained glutamic acid is the quantitatively most important, the proportions of amino acids in the dry matter are as follows.

Like yeast, yeast extract relatively rich in vitamins of the B group, which are contained in the product exemplified in the following amounts.

The pricing in trade with yeast extract takes place due to the content of nucleotides. The higher the percentage, the higher the price to be achieved.

Use

As a flavor enhancer

Yeast extracts are used in a variety of foods. Autolyzed yeast is a source of a plurality of amino acids such as glutamic acid (amino glutaric acid ) and salts thereof. Yeast extract has a flavor no E- number (see food additive ) and is considered by the law not as a flavor enhancer, although it contains salts of amino acids such as glutamic acid, chemically identical to the food additive monosodium glutamate (synonym sodium glutamate, sodium L- glutamate monohydrate food additive e 621, Engl. monosodium glutamate, MSG ) are. Furthermore, it also contains purines Dinatriumguanosinat and disodium inosinate, which is why it is often used for seasoning.

Yeast extract contains about seven percent glutamic acid, so as much as for example parmesan.

Other areas of application

For the preparation of pills, yeast extract is a common component.

Yeast extracts are not a natural source of cyanocobalamin (vitamin B12), although many brands of yeast extract their products add this vitamin. If you want to use it for nutritional reasons (eg to supplement a vegan diet ), should follow the manufacturer's nutritional information.

In bacteriology yeast extract is used as a basis for nutrient solutions and solid culture media. It is inter alia an integral part of the LB medium for the culture of bacteria. In particular, its high content of vitamins of group B is of interest.