The fermentation of grape juice makes wine, and the fermentation of corn products is used to produce ethanol fuel.
Yeasts conduct fermentation in the absence of oxygen, so wine is produced in closed containers in order to keep oxygen in the air away from the crushed grapes.2. A process of the nature of that which results from the operation of leaven on dough or on saccharine liquids: The features that are more recognizable in the fermentation process of yeast, enzymes, etc. are an effervescence or bubbling appearance.
Before the rise of modern chemistry, the term fermentation was applied to all elements that produced transformations which presented heat; for example, in Alchemy, it was the name of an internal change supposed to be produced in metals by a fermentation, operating like leaven.
In modern science, fermentation is restricted to a definite class of chemical modifications peculiar to organic compounds, and produced in them by the stimulus of enzymes.
Bread dough, left to itself and kept from contamination by outside influences, will not rise. Add a lump of leaven (from a Latin word meaning "rise"), and bubbles begin to appear, lifting and lightening the dough. The common English word for leaven is yeast, meaning "to boil".
Yeast also speeds up the conversion of fruit juices and grain to alcohol. Here again, the mutations involve the formation of bubbles, so the process is called fermentation, from a Latin word meaning "boil". The yeast preparation is often referred to as "ferment".