Yeast is a form of Fungi used that has been used for centuries for levening in baking and fermenting alcohol.
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 reproduce asexually by budding, although a few do so by binary fission.Yeast size can vary greatly depending on the species, typically measuring 3–4 µm in diameter, although some yeasts can reach over 40 µm
Selecting and Buying
Preparation and Use
Alcoholic beverages are defined as beverages that contain ethanol (C2H5OH).Beverages such as wine, beer, or distilled spirits all use yeast at some stage of their production.Yeast, most commonly Saccharomyces cerevisiae, is used in baking as a leavening agent, where it converts the fermentable sugars present in dough into the gas carbon dioxide. This causes the dough to expand or rise as gas forms pockets or bubbles. When the dough is baked the yeast dies and the air pockets "set", giving the baked product a soft and spongy texture. The use of potatoes, water from potato boiling, eggs, or sugar in a bread dough accelerates the growth of yeasts.
Conserving and Storing
Yeasts are able to grow in foods with a low pH, (5.0 or lower) and in the presence of sugars, organic acids and other easily metabolized carbon sources. During their growth, yeasts metabolize some food components and produce metabolic end products. This causes the physical, chemical, and sensible properties of a food to change, and the food is spoiled. The growth of yeast within food products is often seen on their surface, as in cheeses or meats, or by the fermentation of sugars in beverages, such as juices, and semi-liquid products, such as syrups and jams.