Alcoholic fermentation is the basis of various food industries - brewing, winemaking, alcohol production. This process is of great importance when baking bread, making dairy, dietary products. Alcoholic fermentation involves the conversion of carbohydrates to carbon dioxide, ethyl alcohol and other components. In the process of anaerobic decomposition of more complex substances into simpler ones, energy is released.
The microorganisms that cause this process are yeast, usually from the genus saccharomyces. In a certain environment, some mold fungi and bacteria can provoke alcohol fermentation. The influence of yeast on the development of the process was established by Pasteur. Subsequently, Buchner, Liebig and Lebedev proved that alcohol fermentation is possible without their (yeast) participation or even without the use of cell-free enzyme components obtained from them. The properties of certain pathogenic microorganisms to destroy certain carbohydrates formed the basis for the process of growing a number of bacterial cultures and the identification of pathogens.
Today it has been reliably established that the transition of carbohydrates to other components is a series of redox and other reactions that occur sequentially. There are different types of fermentation. With the help of yeast, the easiest process is for simple sugars - fructose and glucose.
The latter substance is of particular importance. So, when pickling cabbage, milk, cucumbers, lactic fermentation of glucose takes place. The same process occurs during feed silage. If the mass for silage is not compacted enough, then air enters. Under its influence, butyric acid fermentation begins. As a result of this process, the feed becomes unusable.
In the production of beer , alcoholic fermentation of glucose is used.
Maltose, sucrose may also be subjected to the process. Previously, their hydrolysis by yeast occurs. In this way monosugar is formed.
Lactose (milk sugar) can be fermented only by certain types of yeast.
Glycogen, starch and other carbohydrates with a more complex structure are not exposed to the process. Previously, they undergo hydrolysis by the enzymatic or acid method. As a result, they lose their stability and are affected by yeast.
Yeast itself is a fairly common substance in nature. They are found on berries, fruits, grapes. In the summer, they are common in air and soil.
Yeast is divided into wild and cultural. The latter are called those substances that have technical use in accordance with one or another positive quality. So, for example, the substances used in brewing have the ability to lighten beer, giving it an aroma and a pleasant taste. Grape tremors form a special bouquet. Bread yeast is valued for its ability to actively reproduce, as well as for the properties of well loosening the dough. Wild substances have a weaker fermentation ability. They form components that give an unpleasant odor and taste.
The process of converting sugar into carbon dioxide, ethyl alcohol and other components is quite complicated. Together with these substances, fermentation is accompanied by the formation of other by-products. In particular, acetic and succinic acid, acetic aldehyde, and glycerin are formed in a certain volume. Fusel oils are also formed . These components are a mixture of isomers from higher alcohols: butyl, isobutyl, amyl and others. In addition, substances are formed that, even in negligible amounts, can affect the aroma, give a specific taste to beer, wine and other products.