Alcohol is made from sugar. Every alcoholic beverage, from beer to whiskey to wine, starts with a sugar source that yeast consumes and converts into ethanol and carbon dioxide. The sugar can come directly from fruit, or it can be unlocked from the starches in grains like barley, corn, and rice. That single biological process, fermentation, is the foundation of every drink on the shelf.
How Yeast Turns Sugar Into Alcohol
The species responsible for nearly all drinkable alcohol is a microscopic fungus called Saccharomyces cerevisiae, the same yeast used in bread baking. When yeast cells encounter sugar in a liquid with limited oxygen, they break each sugar molecule apart and reassemble the pieces into two smaller molecules of ethanol and two molecules of carbon dioxide gas. The process is chemically balanced: nothing else needs to be added, and no energy from the outside is required to keep it going once it starts.
This is why you see bubbles rising in fermenting wine or beer. That visible fizz is carbon dioxide escaping. The ethanol stays dissolved in the liquid, gradually increasing in concentration until either the sugar runs out or the alcohol level gets high enough to kill the yeast, usually somewhere between 12% and 18% alcohol by volume.
What Each Type of Alcohol Is Made From
Different drinks start with different sugar sources, and that starting ingredient is what gives each category its identity.
- Wine comes from grapes. Grape juice is naturally high in sugar, so yeast can ferment it directly without any extra processing.
- Beer comes from grains, most commonly barley, but also wheat, rice, and corn. Grains store their energy as starch rather than sugar, so they need an extra step before yeast can work on them.
- Cider comes from apples. Like grapes, apple juice contains enough natural sugar to ferment on its own.
- Sake comes from rice. Despite often being called rice wine, sake uses a mold rather than malting to break down rice starch into sugar.
- Rum comes from sugarcane or molasses, both of which are extremely sugar-rich.
- Whiskey comes from grains: corn for bourbon, barley for Scotch, rye for rye whiskey.
- Vodka can be made from almost anything starchy or sugary: potatoes, wheat, corn, grapes, or even sugar beets.
- Tequila and mezcal come from the agave plant, whose core is roasted to convert its complex carbohydrates into fermentable sugar.
Tropical and traditional drinks expand the list further. Palm wine is made from the sap of palm trees. Mead is made from honey. In parts of South America, chicha is traditionally made from corn. If a plant stores energy as sugar or starch, someone has almost certainly fermented it.
The Extra Step Grains Require
Fruits are easy to ferment because their sugars are already in a form yeast can eat. Grains are harder. The energy in barley, wheat, or corn is locked up as starch, which is a long chain of sugar molecules bonded together. Yeast cannot break those chains on its own.
The solution is a process called mashing. Grain is first malted, meaning it’s soaked in water and allowed to begin sprouting, which activates natural enzymes inside the seed. The sprouted grain is then dried and crushed, mixed with warm water, and held at carefully controlled temperatures, typically around 63 to 68°C (145 to 154°F), for two to three hours. At those temperatures, the enzymes work most efficiently, chopping starch chains into simple sugars. The resulting sweet liquid, called wort in brewing, is then ready for yeast.
Different temperatures during mashing produce different sugar profiles. Holding closer to 60°C yields more simple sugars that yeast can fully ferment, creating a drier, higher-alcohol result. Holding closer to 70°C creates more complex sugars that yeast cannot fully consume, leaving a sweeter, fuller-bodied drink.
How Distillation Concentrates Alcohol
Fermentation alone can only produce so much alcohol. Spirits like whiskey, vodka, rum, and gin all go through an additional step: distillation. This works because ethanol boils at 78.5°C while water boils at 100°C. By heating a fermented liquid, the ethanol vaporizes first, rises into a cooling tube, and condenses back into a much more concentrated liquid.
There is a physical limit to this process. A mixture of 95.6% ethanol and 4.4% water forms what chemists call an azeotrope, a combination that boils as a single substance at 78.2°C. No amount of repeated distillation can push past that 95.6% ceiling. Producing anything purer requires chemical methods beyond simple heating and cooling. For drinking purposes, this limit is irrelevant since spirits are typically diluted back down to 40% to 50% alcohol before bottling.
What Else Fermentation Produces
Ethanol and carbon dioxide are the main outputs of fermentation, but yeast also generates hundreds of other compounds in small quantities. These are collectively called congeners, and they include higher alcohols, esters, and organic acids. Congeners are responsible for much of the flavor and aroma that distinguishes one drink from another. A bourbon’s vanilla and caramel notes, a red wine’s fruity complexity, and a Scotch’s smoky character all depend partly on which congeners are present.
The type of yeast strain, the fermentation temperature, and the available nutrients all influence which congeners form. For example, certain yeast strains produce more of a compound called 2-phenylethanol, which has a rose-like aroma, while others produce more acetic acid, which tastes sharp and vinegary. Winemakers and distillers choose specific yeast strains and fermentation conditions to shape these flavor profiles deliberately.
Congeners also play a role in hangovers. Darker spirits like bourbon and brandy contain higher concentrations of congeners than lighter ones like vodka, which is one reason darker drinks are often associated with worse morning-after symptoms.
Industrial Alcohol From Petroleum
Not all ethanol comes from fermentation. Industrial ethanol, the kind used in hand sanitizer, solvents, and fuel, is often made synthetically by combining ethylene gas (a petroleum byproduct) with water at high temperatures and pressures. This reaction takes place around 260 to 315°C (500 to 600°F) at roughly 1,000 psi of pressure, using a phosphoric acid catalyst to force the ethylene and water molecules together.
Synthetic ethanol is chemically identical to fermented ethanol, but it is not used in beverages. It is typically denatured, meaning small amounts of toxic or foul-tasting chemicals are added to make it undrinkable, which exempts it from alcohol taxes. Fuel ethanol, by contrast, is mostly made through fermentation of corn in the United States and sugarcane in Brazil. Global production reached over 31 billion gallons in 2024, the vast majority of it destined for blending with gasoline rather than for drinking.
Methanol: A Different Alcohol Entirely
Methanol is the simplest alcohol molecule, and it is highly toxic even in small amounts. It has historically been produced through the destructive distillation of hardwoods like beech, birch, and maple, which is why it’s sometimes called “wood alcohol.” Modern industrial methanol is made synthetically by passing carbon monoxide and hydrogen gas over a heated catalyst under pressure.
Methanol is relevant to beverage alcohol because small amounts of it form naturally during fermentation, especially when fruit pulp, skins, and seeds are present. In properly made commercial drinks, methanol levels are far too low to cause harm. The danger arises with improperly distilled homemade spirits, where methanol can concentrate to dangerous levels if the distiller doesn’t separate the earliest portion of the distillate, which contains the most methanol. This is the origin of stories about moonshine causing blindness.