Baker's Yeast (Saccharomyces cerevisiae) is a single-celled microorganism with about 50% protein, high amino acid content, rich in B vitamins, abundant enzymes and a variety of physiologically active substances with high economic value.
Thousands of years ago, humans used Baker's Yeast to ferment bread and wine. In the modern food industry, it is widely used as an excellent leavening agent and nutrient for human staple foods such as bread, steamed bread, buns, biscuits and pastries.
Overview:
The baker's yeast belongs to the genus Saccharomyces and Saccharomyces cerevisiae in the taxonomy of microorganisms. Yeast is a single-celled eukaryotic microorganism. The cell morphology is divided into round, oval, elliptical or sausage-shaped. The size varies with the species of bacteria, and the elliptical is better. The yeast varieties used in bread production have been specially bred and have good gas production and fermentation properties
The role of baker's yeast:
Baker's yeast is the most important microbial starter and biological loosening agent in the bread production process, and it plays a key role in the bread production.
As a food additive, baker's yeast can use the nutrients in the dough to ferment, produce CO2, alcohols, esters and other flavor components, make the dough bulky and elastic, and give the bread its unique color, fragrance and taste It is widely used in bread, pastry and other pastry making with outstanding advantages such as improving the nutritional value of dough and human nutrition absorption and utilization.
Mechanism of baker's yeast fermentation dough:
After baker's yeast is added to the dough, it starts to grow and multiply at a suitable temperature. It benefits first
The monosaccharide and sucrose in the dough are used to produce CO2 gas and various fermentation products. While the yeast is growing and fermenting, the β-amylase in the flour converts the starch in the flour into maltose. The increase of maltose provides usable nutrients for the further growth and fermentation of yeast. Yeast cells secrete maltase and sucrase, and decompose maltose and sucrose into monosaccharides for use. Yeast uses these sugars and other nutrients to carry out aerobic respiration and anaerobic respiration successively to produce CO2, ethanol, aldehydes and ketones, and lactic acid. [1]
The generated CO2 gas is surrounded by the gluten in the dough, so it is not easy to escape and stay in the dough, which makes the dough gradually expand. When baking bread, because the CO2 in the dough expands and escapes, the bread is filled with pores and forms a sponge. Ethanol, aldehydes, ketones and lactic acid are produced during fermentation to form a good flavor of bread.
Types of baker's yeast on the market currently :
Baker's yeast includes fresh yeast and active yeast. According to the different sugar content of the dough, it can be divided into high-sugar yeast, low-sugar yeast and non-sugar yeast. The production of baker’s yeast uses molasses as the raw material. After the yeast is ventilated and fermented, the product with a moisture content of 71%-73% is obtained by separating, washing, and squeezing fresh yeast. The fresh yeast is worthy of granulation and drying. Yeast with moisture content of 7-8.5% is active dry yeast. When low-sugar yeast is fermented, the dough generally contains about 7% sugar, and when high-sugar yeast is fermented, the sugar content is 16%.
There are four main types of baker's yeast used in the food industry: 2/4 fresh yeast is also called pressed yeast, with a water content of about 70%. It is a yeast strain that is grown, propagated, separated, and pressed in a medium such as molasses. production. The advantages of fresh yeast: high activity, stable quality, strong fermentation power, fast fermentation speed, and strong fermentation endurance. In particular, the bread has a good flavor and strong aroma, and is easy to use and relatively inexpensive. Disadvantages of fresh yeast: its activity and fermentability are slightly lower than that of dry yeast, the activity is not stable enough, the storage conditions are strict, the storage time is short, it is not easy to transport for long distances, and it needs to be activated before use. [1]
Active dry yeast is made by squeezing fresh yeast into short strips or fine granules, and then drying at low temperature to make dry yeast with a water content of about 8%. Compared with pressed yeast, the advantages of dry yeast are: transportation is more convenient than fresh yeast, and long-distance transportation does not require refrigerated trucks; it has high activity and stable activity. Therefore, the usage amount is also very stable; the fermentation power is greater than that of fresh yeast. Fermentation endurance is greater than that of fresh yeast; low temperature storage is not required, and it can be stored at room temperature for about 1 to 2 years, and it is not easy to deteriorate. Disadvantages of dry yeast: it must be activated with warm water before use to restore its activity; the fermentation speed is slower and the fermentation time is long; it is inconvenient to use and the cost is higher.
Instant Active Dry Yeast The instant active dry yeast produced by genetic engineering and modern drying technology can preserve its vitality well. The water content is 4%~6%, and the appearance is fine granular. Compared with ordinary active dry yeast, its activity is particularly high, the activity is particularly stable, and the fermentation speed is fast. It does not need to be activated with warm water when used, and does not need to be stored at low temperature. The disadvantage is that it is easy to oxidize and must be stored in nitrogen or vacuum.
The fermentation performance index of baker's yeast:
Proliferation rate: the change in the amount of baker's yeast after being cultured on standard YPD medium for a certain period of time, usually expressed by the change in A660. The baker's yeast with low proliferation rate has no practical value. Gas production: Affect the structure and looseness of bread. Delay period: affects the fermentation speed of the dough, and baker's yeast with a long delay period has no practical value. Sucrase activity: affects the fermentation speed of sugary dough. Maltase activity: affect the fermentation speed of sugar-free dough. Hyperosmotic resistance: affect the fermentation speed of high-sugar dough. Acid resistance: affect the fermentation speed of acid dough. Flavor: Affect the flavor and mouthfeel of bread.
About Bailin Group:
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