How many types of alcohol are in wine?

From ethanol to glycerol: The alcohols that shape wine

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Chemical formula of ethanol molecule
Chemical formula of ethanol molecule

In wine, there are several types of alcohols produced during the fermentation process, which is the transformation of grape juice into wine. This process occurs when yeasts consume the sugars present in the grape must, releasing carbon dioxide and various types of alcohols. The most important alcohols found in wine include ethanol, methanol, glycerol, and other polyalcohols.

The primary type of alcohol in wine is ethyl alcohol, also known as ethanol, which is the main compound responsible for the intoxicating effect. The concentration of ethanol in wine varies depending on the type of grape and fermentation conditions. Table wines usually contain between 7% and 14% ethanol by volume, sparkling wines between 11% and 13%, fortified wines such as sherry between 16% and 18%, and dessert wines typically have ethanol levels below 17%. The ethanol content is commonly measured by determining the boiling point of the wine.

Methyl alcohol, or methanol, is another type of alcohol found in wine, but in much smaller quantities. Unlike ethanol, methanol is not produced directly by fermentation but rather through the enzymatic breakdown of pectins in the grape skins. Red wines tend to have slightly higher methanol levels than white wines, as they spend more time in contact with the skins during fermentation. Methanol is highly toxic in large quantities, but the levels found in wine are negligible and considered harmless.

Glycerol is a significant polyalcohol in wine that contributes to its sweetness and body. It is a by-product of fermentation, with its concentration influenced by fermentation temperature and overall alcohol content. Higher fermentation temperatures and higher alcohol levels typically result in more glycerol production. Glycerol content is also higher in red wines than in white wines. It has a sweet taste and gives wine a smooth, viscous texture, often seen as "tears" or "legs" on the inside of a wine glass.

Erythritol and other polyalcohols, such as arabitol, manitol, sorbitol, and inositol, are also present in wine in smaller amounts. The presence of these polyalcohols depends on the strain of yeast used during fermentation. For example, wild yeast species like Kloeckera apiculata tend to produce more erythritol compared to the common Saccharomyces cerevisiae. These compounds contribute additional sweetness to the wine and are more prominent in wines affected by noble rot caused by the fungus Botrytis cinerea.

Each of these alcohols plays a role in the wine's aroma, texture, and overall sensory profile, making them important components of the winemaking process.

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