Why wine bottles are sealed with cork -- and why that may not be the best material

WineTobias Toft/FlickrA bottle of red under a screw top.

While browsing for wines, your instinct may be to reach for the bottles that require a corkscrew rather than those with a screw cap.

But which is actually better: bottles under cork, or bottles under screw cap?

Business Insider recently spoke with James Harbertson, a Washington State University professor of enology — that’s the study of wine — to ask him some of our most embarrassing questions about wine. On the topic of screw-cap wines, his answer was clear: No, they are not inferior to corked wines, and in some ways might actually keep your wine from spoiling.

While many bulk wines use screw caps — which is likely where the stigma originated — a screw cap is by no means and indicator of the quality of your wine.

In fact, any high-end wines also bear a twist-able top. For example, New Zealand has been transitioning to the twist-off style in recent years. Harbertson said that the screw-top is just as effective as cork at keeping air out.

Why wine bottles typically use cork

There are lots of reasons to use cork instead of a screw-cap. Cork is made from bark, which makes it a renewable resource. Plus, it can form to the shape of a wine bottle, making it an incredibly appealing way to seal wine.

But there’s a drawback: Occasionally bad cork can get into the wine, something called “cork taint.” It’s not going to harm you necessarily, but it will make the wine taste or smell a little funky, like moldy cardboard. Some people are fine drinking that wine, but others — like Harbertson — can’t stand it. It’s why New Zealand decided to switch from cork to screw after getting fed up with bad cork that kept causing this cork taint.

And interestingly enough, a 2013 study that looked into why cork tainted wine smells so bad found that it was because a certain chemical called “2,4,6-trichloroanisole” that’s known to induce cork taint actually suppresses smell rather than create the off-putting odor.

So in the end, going for the screw-cap style wine bottle might be the safest way to go. Unless you’ll terribly miss the pop of a cork coming unstopped.

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