Through the Grapevine

In this multimedia series, we give you the insider's eye on Indiana wines. Tune in each Tuesday for a snobbery-free exploration of a host of viticulture and enology topics.

​​​​​Week 8: Detecting Defects

By Natalie van Hoose

You pop the cork, and a moldy odor fills the air. Or you spy what appear to be splinters of glass swirling in your drink. What gives? Purdue professor of enology Christian Butzke discusses four wine flaws and explains which are merely aesthetic and which should send you down to the cellar for a fresh bottle.

Purdue professor of enology Christian Butzke explains cork taint, a defect that causes strong off-odors in wine.

Cork taint

If you detect a musty, moldy smell in your wine, the culprit could be 2,4,6-trichloroanisole (TCA), a malodorous chemical compound that causes cork taint. TCA can form when natural bark corks are lightened with chlorine bleach; the chlorine reacts with mold to produce TCA, which is extraordinarily powerful even in small amounts.

"A teaspoon of TCA could spoil all the wine that is produced in the entire United States in any given year," says Butzke. "It's one of the most potent odorants that we have in nature."

But the trouble with cork taint is not only its offensiveness to the nose. It can also mask the rich and varied aromas that make wine unique.

"It can make wine smell less interesting, and that's not what a winemaker wants," Butzke says. "I want people to smell and enjoy the wine exactly like I made it. I don't want the closure to affect any of the quality."

But what was once a common problem is on the decline, thanks to a reduced use of chlorine bleach as well as an increase in the use of alternative bottle closures such as screw caps and synthetic corks.

Now only about one in 100 bottles is tainted, says Butzke.


Oxygen is no friend of wine. It can destroy wine's delicate aromas and also causes the color of white wine to darken and brown. But while winemakers take measures to limit their wines' exposure to oxygen during the winemaking process, all bets are off once you open a bottle of wine at home.

This is why Butzke recommends consuming an opened bottle of wine as soon as possible; white wine should be drunk within 24 hours of being opened, and red wine should be consumed within a week (if you can wait that long). Store both reds and whites in the refrigerator after they have been uncorked, and let reds warm back up to room temperature before you drink them.

And don't waste your money on wine-preserving contraptions.

"Once the first glass is poured, air enters the bottle, and the damage will come from that," Butzke says. "That’s why a lot of little gadgets, pumps and gas bottles and all that don’t help much. The air has already gotten into the bottle and been absorbed by the wine."

To guarantee the best quality when ordering a glass of wine at a restaurant, Butzke recommends that you make sure the wine comes from a freshly opened bottle.

Purdue professor of enology Christian Butzke discusses naturally-occuring wine flaws such as "wine diamonds" and protein haze.

Tartrate Crystals

Romantically known as "wine diamonds," tartrate crystals form when the potassium salt of tartaric acid—the main component responsible for the tartness of wine—deposits on the bottom of the bottle or the cork, often as a result of storing the wine at very cold temperatures. These crystals are usually removed by the winemaker from the fermentation tank before bottling but may on occasion find their way into a bottle of wine.

If you do find them in your glass, don't be alarmed.

"They look a bit like glass, but they're harmless," Butzke says. "And they don't taste or smell like anything, so they don’t really affect the quality of the wine. Take them as an indicator that wine is a very natural product."

Protein Haze

If your wine looks hazy, it may be a sign that the natural proteins in the grapes have lost their solubility in the alcohol-rich wine. Like tartrate crystals, however, this wine flaw is purely cosmetic and a sign of minimal processing of the wine by the winemaker: protein haze will not alter the taste or the aroma of the wine.

The winemaker can prevent protein haze by adding natural clay during the winemaking process. The clay pulls the proteins down to the bottom of the tank or barrel, and the refined wine can be siphoned away from the sediment.

"Wine defects do happen, but I think that's the exciting part about wine," Butzke says. "Every wine is unique, and that's part of the thrill in opening a new bottle of wine. You never know what you’re going to get."

Credits: Video by Kelsey Getzin. Web version by Andrew Banta. Through the Grapevine graphic by Russ Merzdorf.

Next Tuesday: If the thought of choosing wines for the holidays makes you tremble, relax! Whether you're new to the wine aisle or trying to please picky guests, our wine-buying guide for the frightened is designed to put the fun back into selecting wine.

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