Dear Dr. Vinny,
Why did the cork start to pop out of a bottle of white wine in my cellar?
—Billy, Roseville, Calif.
Dear Billy,
There are a few reasons why a cork might start protruding, and unfortunately, most of them are not good news.
First off, it could simply be that the cork wasn’t put in the bottle correctly. It doesn’t happen very often, but sometimes I come across a cork that seems like it was put in a bit wonky. If there’s no sign of leakage, and it appears there’s enough of the cork protecting the wine in the bottle, the wine should be alright.
The next concern I would have is that there is some sort of microbial spoilage (or even a refermentation) happening in the bottle. That could cause carbon dioxide to build up and start to push the cork out.
This is typically not a concern with commercially made wine, but with some styles of winemaking—including low-intervention methods—it is a possibility. For example, sulfur dioxide is in all wines as a byproduct of fermentation, and many winemakers decide to add additional sulfur to prevent yeast and bacteria from having a party in the bottle. Many low-intervention winemakers would eschew that practice, and probably also choose not to fine or filter the wines. Both things leave more wiggle room for undesirable yeasts and bacteria to run amok.
If that’s the case with your bottle, the only way to tell for certain is to open the bottle and see for yourself. If it’s a fizzy, yeasty smelling mess, some kind of spoilage probably occurred. The wine isn’t poisonous, but it’ll probably be pretty unpleasant. I wouldn't recommend drinking it unless you’re a huge fan of kombucha. If you don’t open the bottle and it is indeed a science experiment happening in there, there’s a very slim chance the carbon dioxide could build up to the point that the cork shoots out or the bottle explodes.
My next concern is a temperature fluctuation, particularly heat. When a bottle of wine warms up, the pressure inside the bottle will build up and cause the wine to push up against the cork. Sometimes you’ll actually see signs that the wine leaked out—usually the top of the cork will be sticky or discolored. But leakage can also be from cold temperatures. If a wine is exposed to freezing temperatures, the water component of the wine can start to freeze and crystallize, which causes the liquid to expand and start to put pressure on the cork.
Either way, the main issue with leakage is that when wine leaks out, air gets in. Air inside the bottle can cause your wine to become oxidized. Heat is also a major concern because there’s a chance that the wine was also “cooked” along the way, which means what it sounds like. The fruit flavors could take on stewed or baked flavors and the wine will seem tired.
Again, the only way to tell is to open the bottle and taste it!
—Dr. Vinny
