Alcoholic Fermentation - Yeasts (2)
When the sugar content in the medium is high, as in the case of syrups or molasses, yeast survival is affected during the process of converting sugar to alcohol due to the sugar concentration, usually measured in degrees Brix. High sugar concentrations slow down the osmotic processes of cell membranes, making fermentation difficult.
Different types of yeasts have different levels of tolerance to sugar and ethanol concentrations, and in the case of wine yeasts, the limit is usually around 14% alcohol. The sugars most commonly used in fermentation are dextrose, maltose, sucrose, and lactose.
Yeasts specifically target each carbohydrate, and maltose is the most affected. The number of yeasts is also a crucial factor, which is determined by counting them in the laboratory or in the industry, often with the help of Neubauer chambers.
Although some enzymes such as diastase and invertase are involved in fermentation, it is zymase that is exclusively responsible for the conversion of carbohydrates to ethanol and carbon dioxide. This albuminoid substance found in yeast cells directs the biochemical reaction that transforms glucose into ethanol.
The idea that a specific substance in yeast cells could produce fermentation was first proposed in 1858 by Moritz Traube, known as the enzymatic or fermentative theory, and was later supported by Felix Hoppe-Seyler. However, Eduard Buchner’s discovery that fermentation occurred without the participation of yeast cells and fungi put an end to this theory.