What Is Yeast?

Answer:

Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with the 1,500 species currently described estimated to be only 1% of all yeast species.

Most yeasts belong to the division Ascomycota. A few yeasts, such as Candida Albicans, can cause infection in humans. The most commonly used yeast is Saccharomyces Cerevisiae, which was domesticated for wine, bread and beer production thousands of years ago.

The typical yeast cell is approximately equal in size to a human red blood cell and is spherical to ellipsoidal in shape. Because of its small size, it takes about 30 billion yeast cells to make up to one gram of compressed baker’s yeast.

Yeast reproduces vegetative by budding, a process during which a new bud grows from the side of the existing cell wall. This bud eventually breaks away from the mother cell to form a separate daughter cell. Each yeast cell, on average, undergoes this budding process 12 to 15 times before it is no longer capable of reproducing.

During commercial production, yeast is grown under carefully controlled conditions on a sugar containing media typically composed of beet and cane molasses. Under ideal growth conditions a yeast cell reproduces every two to three hours.

If the organisms receive enough food and air, and are at a comfortable temperature, they reproduce very quickly. In bread, this causes the dough to rise, as single cells are replaced by huge clusters. When bread dough is punched and worked after the first rise, it distributes the organisms evenly, so they continue to ferment.