At some point, being a wine enthusiast means coming to terms with flaws. Terms like TCA, VA, brett and premox.

Anyone who pops a goodly number of corks will probably have encountered these and/or other defects. Often such experiences are just written off as crummy wine (not good news for the winery). And sometimes a small amount of imperfection is just fine: I can happily sip a wine with very slight cork taint, while others can’t go near it. I like and even expect a little brettanomyces in wines from the Rhône region.

But if a wine smells like a wet newspaper, Band-Aid or nail polish remover, not to mention rotten eggs, it is indeed flawed and nigh on to undrinkable. Here’s a look at a variety of wine flaws and how to detect them:

Cork taint: Caused by a chemical compound within the cork called 2,4,6-Trichloroanisole (thus, TCA), this is present in 3 to 5 percent of wines with a cork closure, so most wine consumers have encountered it whether they knew it or not. Sometimes the wine is undrinkable; other times it’s just “off,” with subdued fruit. Musty, moldy odors — like wet newspapers or a damp basement — are a telltale sign. TCA is the reason we’ve seen so many alternate closures (screw cap, glass, plastic) in recent years.

Volatile acidity (VA): Wine is 80-plus percent water, combined with countless chemical components. Some of those components are acids, most of which are not of the volatile ilk. But too much acetic acid produces a vinegary aroma, and ethyl acetate (aka acetone) has a harsh, nail-polish-remover odor. Not exactly conducive to a pleasurable experience.

Oxidation: This occurs when exposure to oxygen contaminates phenols or other components. It can happen at any point in the fermentation process or even in the bottle. It will happen if you open a bottle, have a glass or two, and reseal it for a week. Oxidized wines lose color — reds start to go brown; whites get murky — and flavor, so the eyes and the palate rather than the nose are where this flaw will show up. Vintners in Burgundy have been battling premox (premature oxidation) in their white wines for years.

Reduction: The opposite of oxidation, in that too little oxygen exposure can cause problems. Foremost among them: Certain sulfurs can produce aromas of rotten eggs or even sewage. There’s a fine line here because, like oxidation, reduction can be an essential aspect of a winemaker’s style. But the process can prompt the stinkier sulfurs to come to the fore.

Maderization: The method used to make the marvelous dessert wines from Madeira — slowly cooking them for an extended period — will ruin table wines that have been stored in not-cool-enough spaces. I learned this the hard way with some stellar 1989 Châteauneuf-du-Papes left too long in a warm basement. Sigh. These wines will turn brown and smell like other dark alcoholic beverages (bourbon, sherry) but not like wine.

Brettanomyces: This yeast strain can actually be a good thing in small doses, adding complexity to a wine’s aromas and flavors. But there’s a difference between a meaty, smoky or leathery wine and one that smells like dirty gym clothes or a barn overdue for a cleaning. Sometimes brett can produce a medicine-y, Band-Aid-like odor.

So what to do with wines such as these? In a restaurant they can be sent back, but first consult with a server or manager to confirm your diagnosis. Flawed wines purchased at stores can be returned, but usually only if purchased relatively recently.

In any event, the bottle needs to be fairly full. If you drank most or all of it, that’s called a learning experience, and not so conducive to a refund.


Bill Ward writes at Follow him on Twitter: @billward4.