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Alcohol and Its Role in Wine
Alcohol is, of course, one of the most critically important components of a wine. To kick off 2025, let’s discuss where alcohol in wine comes from, what role it plays, and how it can be adjusted.
Where Does Alcohol Come From?
Alcohol derives from the sugars in grapes, which are constructed through the process of photosynthesis. During photosynthesis, the vine captures sunlight, water, and carbon dioxide and creates sugar and oxygen. After veraison (the point midway through the growing season when grapes shift from green to red or yellow), the sugars are moved from the leaves to the berries. This process of ripening continues until harvest as the grapes accumulate more and more sugars.
The amount of sugar a grape accumulates is directly proportional to its potential alcoholic strength. Sugar accumulation depends on both the grape variety and the climate. Certain varieties simply accumulate more sugar than others. Further, grapes can achieve greater ripeness with increased access to sunlight, amplified even more by heat. For this reason, warm, sunny regions tend to produce more alcoholic wines than cool, cloudy ones. Desired alcohol level in a wine is a key consideration when choosing a harvest date. Winemakers wanting fuller, higher alcohol wines may allow grapes to hang longer on the vine than winemakers seeking lighter, lower alcohol styles.
During the fermentation process, wine yeasts convert the sugars in the grape must into alcohol (specifically ethanol) and carbon dioxide. It is during fermentation that juice is transformed into wine. Most wines naturally fermented to dryness contain around 12-15% alcohol by volume (ABV). That three percent range may seem small, but the sensorial effects of a 12% ABV wine versus a 15% ABV wine can be dramatic.
What Role Does Alcohol Play in Wine?
While colorless and odorless, alcohol is one of the most critical structural components in wine. Alcohol serves as an important preservative, creating an inhospitable environment for various bacteria and spoilage yeasts that can ruin a wine. While generally flavorless, alcohol has a slight perceived sweetness and provides a general warming sensation, helping craft the balance and mouthfeel of a wine. In all, alcohol helps uphold the structure of a wine, and its presence is one of the pillars that allows a wine to age with grace.
Of course, alcohol is also an intoxicant. While wine media and literature rarely celebrate wine’s inebriating effects, certainly this has been one of wine’s major draws for millennia of consumers. Nevertheless, there are various methods for removing alcohol partially or entirely from a wine, and various “low-alc” and “no-alc” wines have gained in popularity over the last few years.
Can Winemakers Change the Alcohol in Wine?
Yes, there are many opportunities for a winemaker to adjust the amount of alcohol in a wine. Winemakers looking to increase ABV may choose to add additional sugar to the must, a process called chaptalization, thereby giving the yeasts more material to convert into alcohol. While less widespread than it once was, chaptalization is still practiced in many cooler winegrowing regions, especially in cold and rainy vintages. A more extreme option is to simply add alcohol to a wine, typically in the form of brandy, through a process called fortification. Port, Sherry, and Madeira all rely on fortification to create their unique styles and raise their ABVs as high as 20%. For each of these historic categories, such high alcoholic strength allowed their export far and wide without spoilage.
