Yeast Extract is a yeast derivative, rich in various amino acids, vitamins and trace elements and other nutrients, so it is widely used in food additive, biopharmaceutical, fermentation and other fields. This article combines multiple papers to explain the definition, source classification of yeast extract, as well as briefly introduce its production process, nutritional ingredients, possible mechanisms, etc. Then, the concept of yeast powder is introduced: compared with yeast extract, yeast powder contains intact cell walls, protein and other nutrient components which are not fully degraded, and it is suitable for microbial fermentation with strong protease secretion ability. I hope that the above content is of guiding significance to all fermentation engineers and researchers.
Concept
What is yeast extract? Yeast extract, derived from yeast, utilizes biotechnology to degrade the protein and nucleic acid in the cell under a specific environment, and then prepared as a soluble nutrient source through downstream processing operations such as centrifugation, concentration, filtration, etc. Yeast extracts are usually preserved in paste or powder form. In 1997, the International Hydrolyzed Protein Committee (IHPC) stipulated that the main components of yeast extracts include amino acids, peptides, polypeptides and water-soluble components of yeast cells produced by the decomposition of peptide bonds through natural enzymes which present in edible yeast. Yeast extract can be in the form of liquid, Paste, powder or granules.
Features
● Rich in nutrients such as protein, amino acids, peptides, nucleotides, Vitamin B group, growth factors, trace elements, etc., of which the proportion is harmonious to provide comprehensive and balanced nutrition for microbial fermentation and propagation.
● Meet the increasing demands of the biological industry for organic nitrogen sources, and provide the necessary guarantee for the clean production of fermentation industry.
Classification of biological sources
1. Baker’s yeast extract
Using purely natural high-protein baker's yeast as raw material, the product is rich in nutrients and no impurities, light in color, good in solubility, and easy to extract after the product. It has the characteristics of high efficiency, cleanliness, safety and stability, and meets the safety standards of food and medicine.
2. Brewer’s yeast extract
It uses the by-product beer mud as the raw material after brewing beer, and has certain impurity components. The color is darker and the solubility is not good. The product is rich in nutrition and low in cost. It is suitable for the fermentation of non-food and pharmaceuticals that do not require high cleanliness and safety.
3. Torula yeast extract
Torula yeast extract, from Torula yeast, with high protein content, dark color, common solubility, and speical odor. Torula has strong growth and reproductive ability, and is only suitable for fermentation production without cleanliness and safety requirements.
Production method of yeast extract
1. Acid hydrolysis
Acid hydrolysis is the use of acidic substances to break down yeast cells (mainly using sulfuric acid or hydrochloric acid). However, the post-processing cost of this method is high and the pollution is heavy, so it is basically no longer used in the industrial production of yeast extract.
2. Enzymatic hydrolysis
The enzymatic hydrolysis method is breaking down the yeast by the action of the added enzyme. The technological process is as follows: the enzyme in the yeast cell is inactivated by heating and other methods, and then the exogenous enzyme is added under certain conditions, the content of the yeast cell itself is released under the stimulation of the exogenous enzyme, and is decomposed into small molecules such as amino acids. Then use the downstream process to process the yeast liquid to obtain yeast extract. The advantage of this method is that the obtained yeast extract is of good quality, but it has high requirements for enzyme preparations, so the production cost is high, and it is not commonly used at present.
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