Alcohol obtained by fermentation, such as that found in wine, beer, or cider, is formed through a biological process in which microorganisms transform sugar into ethanol (alcohol) and carbon dioxide.
The raw material must be rich in sugars or starch. This can be fruits (grapes, apples, etc.), which are rich in directly usable sugars, or grains (barley, corn, etc.), which contain starch, which must first be transformed into simple sugars using enzymes (malts or enzymatic treatments).
Microorganisms are yeasts. The most commonly used are yeasts of the genus Saccharomyces (such as S. cerevisiae). They feed on sugar and produce ethanol + CO₂ in an oxygen-free environment (anaerobic fermentation).
The alcohol content increases up to a certain point (usually 12–15%): beyond this point, the alcohol kills the yeast. Some products (beers, wines) undergo maturation to develop their aromas.
To obtain stronger drinks (whiskey, rum, etc.), the liquid is then distilled to concentrate the ethanol.
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The history of fermentation is almost as old as humanity itself—it's one of the oldest known food processing techniques.
Early humans likely discovered fermentation by leaving fruit juice or grain soaked in the open air, where wild yeasts began converting the sugars into alcohol or acids. The earliest archaeological evidence dates from around 7000 BC in China (fermented rice residue, honey, and fruit). Beer and wine were being made in Mesopotamia and Egypt as early as 3500 BC.
Fermented wine, sometimes flavored with herbs or honey, was made in Greece and Rome since ancient times.
European monasteries perfected beer and winemaking throughout the Middle Ages.
