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What is yeast?

2017-05-27

People have been using yeast for a long time, but people used to know merely how to ferment and not understand how it works. It was not until the late 17th century that the mystery of yeast fermentation was discovered.
Yeast making starts from yeast species. Using starch or molasses as raw material, adding in nitrogenous element, after disinfection, sterile aeration, thermostatic incubation, step expanding, yeast mud collection and prilling, dried on low boiling bed or fluidized bed, and we get the yeast, a pure bio-fermentation agent.
The use of aluminum-plastic film vacuum packaging extends the shelf life of up to 2 years.

Yeast fermentation
Yeast fermentation is complex biochemical changes that convert carbohydrates to CO2, alcohol, a small amount of other alcohols, lactic acid, and energy under appropriate conditions.
Yeast produces large amounts of carbon dioxide gas under suitable conditions, so that the dough leavens into loose and elastic honeycomb bulk.
Compared with other methods of fermentation, yeast has many advantages.

Four functions of yeast in fermentation
1 Biological leavening: In fermentation the yeast produces carbon dioxide that is kept inside the dough by its reticular structure. The dough thus bulks and becomes soft and porous.
2 Dough extending: The yeast also softens the dough so the dough becomes more expandable and air-holding, which is something chemical leavening agents cannot do.
3 Pastry flavoring: Other than carbon dioxide and alcohol, the yeast also produces a variety of volatile and non -volatile compounds during fermentation, adding a unique flavor to fermented bread and pastry.
4 Nutrient adding: Half of the yeast is protein. The yeast contains high amount of amino acid, lysine, vitamin B1, B2, B11 and niacin, improving the nutritional value of fermented foods.

Yeast is usually known as a leavening agent that bulks the dough into soft and porous structure. But it is actually a microoganism and single yeast is not visible to the naked eye
The yeast is a fungus and its cells are similar to those of plants. A yeast cell has cell wall, plasma membrane, nucleus, cytoplasm and other contents. The cytoplasm contains fat particles, starch particles and vacuole
In bread and fermented pastry making, the driving force of dough fermentation comes from the yeast. Therefore the quality of yeast affects greatly the whole making process and the quality of the end product. Poor quality yeast may even cause the whole making to fail. A good choice of yeast is of great importance.

Yeast production process

Normal form of fresh yeast