Fermentations and Biotechnology

The fermentation of carbohydrates by yeasts to produce ethyl alcohol is used by the alcoholic beverage industry. Wine is the aged product of alcoholic fermentation of fruits. The wine-making process begins with crushing and stemming the grapes to produce a product called must (Figure 1 ). Sulfur dioxide is used to kill wild yeast and other organisms, and the must is then combined with species ofSaccharomyces to ferment under carefully controlled conditions. The skins and seeds of grapes contribute to the color and flavor of the wine. Fermentation takes several days and results in a wine having an alcoholic content of about 15 percent. In dry wines, most of the available carbohydrate has been used, while in sweet wines, some carbohydrate remains. 

Figure 1

The process used in the commercial production of wine.