. . . Traditional Home Winemaking from Nature's Harvest . . .
In winemaking, alcohol is produced through a biological process called fermentation, where yeast converts sugars found in fruits into alcohol and carbon dioxide.
The basic process
The fruits naturally contain sugars, mainly glucose and fructose. When yeast is added (or naturally occurring yeast begins growing), the yeast consumes these sugars as food.
Because the fruits contains both glucose and fructose, yeast ferments both sugars through a series of enzyme-catalyzed reactions, but the overall result is approximately the same: sugar is converted into ethanol and carbon dioxide.
A more complete representation shows that energy is also released:
C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂ + energy
The yeast uses some of this released energy to grow and reproduce during fermentation.
This means:
Glucose (sugar) → ethanol (alcohol) + carbon dioxide (CO₂)
The yeast also produces small amounts of heat and many flavor compounds.
What's happening inside the yeast?
Yeast cells use sugar to obtain energy. In the low-oxygen environment of fermenting fruit juice, they perform alcoholic fermentation rather than normal aerobic respiration.
Sugar enters the yeast cell.
The sugar is broken down through a series of biochemical reactions.
The yeast extracts energy for its own growth and survival.
Ethanol and carbon dioxide are released as waste products.
Why does the fermentation stop?
Fermentation usually ends because one or more of these happens:
Most of the sugar has been consumed.
The alcohol concentration becomes high enough to inhibit or kill the yeast.
The temperature becomes unsuitable for yeast activity.
Winemakers intentionally stop the fermentation.
How much alcohol is produced?
A useful rule of thumb is that fruits and sugar are able to reach about 22–25° Brix (22–25% sugar by weight) will typically produce wine containing roughly 12–15% alcohol by volume (ABV).
What happens to the carbon dioxide?
In still wines, the CO₂ mostly escapes into the air during fermentation.
In sparkling wines such as Champagne, winemakers trap the CO₂, creating the bubbles.
Why wine tastes more complex than just alcohol
Yeast doesn't only produce ethanol. During fermentation it also creates hundreds of compounds, including:
Esters (fruity aromas)
Higher alcohols
Acids
Aldehydes
Sulfur compounds
These compounds contribute to the wine's aroma and flavor profile.
In short: yeast eats the sugars, uses part of the sugar for energy, and converts the rest into ethanol (the alcohol in wine) and carbon dioxide through fermentation.
