Why Doesn’t Wine Freeze? And Do Vacuum-Sealing Stoppers Keep Wine ‘Fresh’?
I set out to learn why wine doesn’t freeze. But while I was questioning a wine researcher, I thought I’d also find out whether those vacuum-sealing wine stoppers are worth it. Here’s what I found out.
Question 1: Why Doesn’t Wine Freeze?
Wine will freeze, it just has a much lower freezing point than water – primarily because of its alcohol content. Pure alcohol (ethanol) freezes at approximately -114.7 degrees Celsius (-174.46 degrees Fahrenheit). Most of the wine that you’ll buy at the store probably has an alcohol content of around 13.5 percent, which significantly lowers the freezing point of the vino.
[An aside: wines with a higher percentage of alcohol are less common because once they hit 14 percent they are no longer listed as “table wines” in the eyes of the U.S. Alcohol and Tobacco Tax and Trade Bureau – and that makes them subject to a higher tax rate.]
But alcohol isn’t the only factor when it comes to the lower freezing point for wine. The presence of soluble solids, such as sugars, also plays a role. That happens because the presence of a solute (sugar, for instance) lowers the freezing point of the solvent (such as water).
I’ll explain how that works using sucrose (even though residual sugars in wine are not sucrose) because sucrose is pretty easy to explain. (FYI, residual sugars tend to be glucose, fructose, or sugars the yeast couldn’t digest readily during fermentation).If you dissolved 10 grams of sucrose (table sugar) into 100 grams of water, the freezing point would only go down by one degree Fahrenheit to 31 degrees (or -0.56 degrees Celsius). In other words, you’d need a LOT of sugar to lower the freezing point a significant amount. For more on this “freezing point depression” and other colligative properties, check out this site.
Question 2: Do Vacuum-Sealing Wine Stoppers Keep Wine “Fresh”?
Have you seen these vacuum-sealing wine pumps? The idea, apparently, is that by creating a vacuum in the wine bottle, you can postpone finishing off that bottle of wine without affecting the quality of the wine itself. Does it help? Maybe.
To maintain the quality of your wine, you want to limit its exposure to oxygen. If the vacuum seal helps you do that, great. It’s just not clear whether it works significantly better than, say, jamming the cork back in.
Either way, there are two major reasons why oxygen is bad for wine. First is oxidation, which white wine is more susceptible to. When oxidized, white wine can take on a brownish tint – as well as some off-putting flavors. Red wine is more resistant to oxidation because it contains more anthocyanins and phenolic compounds that can act as antioxidants. Red wine has more of these substances because it is fermented with the skins intact, and the compounds leach from the skins into the wine (generally, only the juice is fermented when making white wine).
The second reason oxygen can be bad for your wine is because most wines contain trace levels of bacteria or yeasts that can turn the ethanol in your wine into acetic acid. These contaminants are usually present in such small amounts that they’re not a problem. But when exposed to oxygen, they can grow – and your wine will be on its way to becoming vinegar (as acetic acid is more generally known).
Note: Many thanks to Dr. Trevor Phister, assistant professor of food science at NC State, for taking the time to talk to me about wine. Any errors in the above post are mine, and mine alone.