There are many types of yeast. Most widely used type of yeast is baker’s yeast, which is also known as brewer’s yeast. Scientifically, it is also known as Saccharomyces cerevisae. Saccharomyces yeast shouldn’t be mixed together with baking soda. Baker’s yeast, which is being sold as dry cubes or granules, consists of alive yeast. Baking sodas are carbonates and bicarbonates and they produce carbon dioxide.
Brewer’s yeast had been used in bread making until 19th century. But today, this usage has disappeared completely. Nowadays, we find the dietary supplement yeast which is being sold as tablets or flakes under the name of “brewer’s yeast”.
Frequently used types of yeast are; sourdough, fresh yeast, instant yeast, liquid yeast and dry yeast.
Sourdough is an old way of turning flour and water into a bread. Fungus and bacterias in the sourdough diffuse into the dough and start living in a suitable environment. In the meantime they store a lot of air in the dough, this way the flat dough starts to expand, grow and becomes a real bread. It’s produced by fermentation. 70 percent of it’s content is water. Under proper circumstances it can last for 3 to 4 weeks.
Instant yeast is in a really thin and granular form. It dissolves in a short time. Water content of it has been reduced to 5 percent. Without the need of adding water it can be used by directly mixing it into the dough. In a cool and dry environment it can last for two months.
Dry yeast is appropriate for home usage. It can be find in little granules and it has a cream color. It’s prepared by dissolving it in a warm water, 15 mins prior to use. In a cool and dry environment, it can last for twelve months.
Liquid yeast can be easily absorbed by the dough. Because of this feature it is mainly used in large bakeries. Liquid yeast is a suspension of yeast cells in water. In yeasts being sold as 500 grams cubes and large bags, yeast cells leave the stock solution at the and of the fermentation. This process is not required for liquid yeast.
Fresh yeast is a type of yeast that can be used in all pastries that require a dough with yeast. It must be stored in a refrigerator. Fresh yeast’s shelf life is generally between 20 to 30 days.