Hello there! I'm Dr. Vinifera, or "Vinny" for short. Ask me your toughest wine questions, from the technical aspects of winemaking to the fine points of etiquette. I hope you find my answers educational and even amusing. Looking for a particular answer? Check my archive and my FAQs. You can also follow me on Twitter: @AskDrVinny.
Dear Dr. Vinny,
After you open a bottle of wine, does the alcohol in it start evaporating? If you leave an open bottle open for three hours, would the alcohol go from 14 percent to 12 or less?
—Daniel A., Panama
Let’s start with how the alcohol content is determined. During fermentation, the sugar in the grapes is converted into alcohol. Once the wine is bottled, the alcohol content doesn’t change any further.
But once you open a bottle of wine and expose it to air, things start to change, and you’re right that evaporation comes into play. Both the water and the alcohol in wine are subject to evaporation, and typically the alcohol will evaporate somewhat faster than the water does. But it really depends on a lot of different variables, including the temperature, the airflow and how much of the liquid’s surface area is exposed to air. Also, the water would evaporate faster in dry air than in humid air.
In most cases, while some evaporation would take place, its effect would be negligible. It would take days, weeks or even longer to get any measurable difference in the alcohol content. Because wine doesn’t have much alcohol in it by volume—typically from about 12 to 16 percent—it’s not going to evaporate nearly as quickly as would the same amount of rubbing alcohol. In fact, wine that’s just sitting there evaporating would probably turn into vinegar before it would become alcohol-free.
If you want to speed up the evaporation of alcohol, you could increase the wine’s surface area, airflow and temperature. You could even put it in a pan and start to heat it up. And if you take three bottles of red wine and heat it, set it aflame and evaporate it by half, you’ll have a terrific red wine reduction sauce to braise short ribs in.
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