Yeast is a single-celled fungus that plays a crucial role in various biological processes, especially in the fermentation of food and beverages. Yeast can be divided into industrial yeast and natural yeast. The most commonly used yeast in daily life is industrial yeast, which can be further divided into two types: active dry yeast, which has a relatively long storage time and stable quality. Another type is fresh yeast, which has a relatively short storage time, high moisture content, and high activity, but requires refrigeration and is more suitable for low-temperature fermentation.

Yeast has many applications, but one of the most well-known is Saccharomyces cerevisiae, which is commonly used in baking, brewing, and winemaking.

Yeast is used in baking to help dough rise. When yeast consumes sugars in the dough, it produces carbon dioxide gas and alcohol through fermentation. The gas gets trapped in the dough, causing it to expand and rise, resulting in a light and airy texture in baked goods.

In brewing, yeast is responsible for fermenting sugars in the wort (the liquid extracted from malted grains) to produce alcohol and carbon dioxide, creating beer. Different strains of yeast can produce different flavors and aromas in the finished beer.

Similarly, in winemaking, yeast converts sugars in grape juice into alcohol and carbon dioxide, turning the juice into wine. Again, different strains of yeast can influence the flavor profile of the wine.

Yeast is also used in the production of other fermented foods and beverages, such as cider, mead, and sake. Additionally, yeast is used in biotechnology and scientific research as a model organism for studying genetics and cellular biology.

Process Flow

Process Description

The production of yeast involves a carefully controlled fermentation process. Here's a general overview of how yeast is produced:

(1) Strains Propagation: Yeast production typically starts with a pure culture of yeast cells. This can be obtained from a yeast bank or a previous batch of yeast.

(2) Preparation of Raw Materials: A nutrient-rich growth medium is prepared. This medium typically contains sugars (like glucose or sucrose), nitrogen sources (like ammonium salts or amino acids), vitamins, and minerals. The exact composition of the medium depends on the specific yeast strain and the desired characteristics of the final product.

(3) Inoculation: The yeast culture is inoculated into the growth medium under sterilization conditions. The culture is then allowed to grow and multiply. This initial growth phase is often carried out in a small-scale laboratory fermenter.

(4)Scaling Up: Once the yeast culture has reached a sufficient density, it will be transferred to a larger fermenter to scale up the production. The fermenter is a large vessel equipped with agitators, temperature control, and aeration systems to provide optimal growth conditions for the yeast.

(5)Fermentation: The yeast culture is allowed to ferment for a specific period, during which it continues to grow and produce more yeast cells. The fermentation process generates heat, so the temperature is carefully controlled to prevent overheating.

(6)Harvesting: After the fermentation is complete, the yeast cells are harvested from the fermenter. This can be done by centrifugation or filtration to separate the yeast cells from the spent growth medium.

(7)Yeast Recovery: The harvested yeast cells are washed and concentrated to remove any remaining raw materials. The yeast cells are then dried or processed into a form suitable for storage and distribution.

(8)Quality Control: Throughout the production process, various quality control methods are conducted to ensure that the yeast meets the desired specifications in terms of purity, viability, and other characteristics.

(9)Packaging and Distribution: The final yeast product is packaged into containers suitable for distribution to customers. This can include dry yeast in sachets or blocks, liquid yeast in vials or pouches, or other forms depending on the purpose.

Overall, yeast production is a complex process that requires careful monitoring and control to ensure the quality and consistency of the final product. Different yeast strains and production methods may result in variations in the final product.