Wine Faults — What is Cork Taint?

There are many benefits of using cork to seal a wine bottle. It is natural, renewable, recyclable, and 100% biodegradable. It is flexible, able to compress and expand to provide a tight seal through temperature fluctuations. And it breathes, allowing the wine inside to age and evolve. Then there’s also the tradition—the ceremony of uncorking a bottle or the celebratory popping of a champagne cork, making it the closure most consumers prefer and expect.

Cork, however, does have its kryptonite: cork taint, also known as 2,4,6-trichloroanisole or TCA. Most commonly, TCA is transferred to wine in the bottle through natural cork. Hence the terms ‘corked’ or ‘corky’. It is a wine fault, causing an off-putting, musty smell and taste in the wine, dulling its character, and weakening cork’s powers as the perfect bottle seal. And learning to identify it means better drinking for you.

What causes cork taint?

TCA is the result of a chemical reaction between fungi naturally present in cork, the plant phenols, and chlorine. In the past, chlorine was used to sterilize corks, while cork trees were also treated with “organochlorine” insecticides. Both of these practices were discontinued by the cork industry in the 1980s, when chlorine was identified as the catalyst to the reaction. However, chlorine residues still remain in the cork forest ground.

New technologies and advances in the manufacturing process and quality control have made strides, but cork taint is not fully eradicated yet, and it may never be. Wine producers (and consumers) who opt for cork must accept that a percentage of their wine may be affected by TCA. 

What does cork taint smell like?

Are you getting musty aromas of damp cardboard, old, mouldy cellar, wet dog, or dank dishcloth? That’s TCA. But that not the whole story—TCA levels can vary in range, as can one’s ability to detect it.

TCA is measured in parts per trillion (ppt). It can usually be detected as low as at five ppt, with some people being sensitive to it at one or two ppt, according to research. Some people can detect it only in higher amounts (100-200 ppt), while others are physically unable to detect it at all. Chalk that up to genetics.

At its highest levels, it is overpowering with the musty smell practically jumping out of the bottle, and able to be easily detected (though perhaps not identified) by even an inexperienced drinker. At lower levels however, it may be more subtle, lurking there under the other aromas. Or there may not be any perceptible mustiness, with the wine simply stripped of fruit and floral aromas and flavours, making it flat, dull, astringent or bitter. In this case, it is easy for consumers to assume that it is simply not a well-made wine, or that they just don’t like that particular wine. 

As mentioned, genetics come into play in one’s ability to detect TCA, and so does experience. Like all wine tasting, the more you practice identifying specific aromas, the better you will become at it. If you get a corked bottle, treat it like a learning moment, small consolation that may be at the time.

TCA FAQs

How common is it?
Estimates vary—billions of bottles of wine are produced each year and many corked bottles may never be identified or reported as corked. Past estimates were as high as one in 10 bottles (10%), but with new cork treatments and technologies the number is now touted to  be around 2–5%, depending on the source, i.e.: the cork industry or the wine industry. Bottom line, it’s still quite common.

Is corked wine ever a good thing? Can it add character to a wine?
No. Unlike some flaws like volatile acidity or brett, where a little taint can add complexity to a wine, cork is always a fault. Even in miniscule amounts, it detracts from the wine, dulling the fruit and floral notes.

Will it blow off if I decant or let it breathe for a while?
No. Though this works for some wine faults, TCA is stable, and can become more prevalent with aeration. If it’s corked, it’s done for.

Do I need to taste the wine?
If you clearly smell cork taint, there is no need to taste the wine, but at lower levels or if you are unsure, tasting can help confirm it. Or you may only detect it upon tasting. Another detection complication? Cork taint itself inhibits olfaction, so sometimes you just get a whiff, then it’s gone. 

Oh no,  I drank it—will corked wine hurt me?
No, the TCA levels found in tainted wine are so low, they are not harmful. Likely it’s your taste buds that will suffer most.

Can I cook with it?
Again, it won’t hurt you, but if a wine is not enjoyable to drink, it won’t be to eat either, especially once the flavours are reduced down
and concentrated in your meal. 

I heard cork taint mostly affects cheaper wines. Is that true?
No, TCA can affect wine regardless of price or quality level. If it has a cork, it’s a potential candidate for taint.

But… I though ‘corked’ meant bits of cork floating in my wine glass ?
No, that is a service flaw, not a wine fault. Fish them out and carry on.

So, I’m out the cost of a bottle of wine?
You can return (full-ish) corked bottles to where you purchased it—your friendly local monopoly (LCBO in Ontario), the wine agent, wine store, bottle shop or restaurant. 

Can I tell if the wine is corked from smelling the actual cork?
The answer to this is somewhat polarizing. Some people recommend always smelling the cork first, while others declare it won’t tell you anything. This may also have to do with perception thresholds or the level of cork taint in the wine. Bottom line—you need to smell (and maybe taste) the wine itself to determine if it is corked, but if smelling the cork helps you hone your TCA detection skills, go for it.

What if my wine has a screw cap—should I still test sniff it before drinking?
Yes. Though rare, ‘cork taint’ can occur in the winery itself—the combination of damp surfaces, sources of phenols such as barrels, pallets, beams, cardboard, and use of chlorine-based cleaning products or chemical treatments, can be ripe for reaction. Plus, TCA is only one possible wine fault. When you smell a wine, you are checking for any fault or flaw, regardless of closure.

So, when a server pours me a sample from the bottle I ordered, it‘s not check if I like the wine?
No, it’s to check whether the wine is clean (i.e.: free of faults) or not. And if there is any doubt, they are there to help you.