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How to Tell if Wine is Corked

How to Tell if Wine is Corked

iLoveWine Staff
A bottle of wine and a cork.

A delicious and enjoyable bottle of wine is something of a chemistry miracle. There are so many factors involved, so many molecular compounds at play, so many ways that things can go wrong, that when they go right, it is undoubtedly a noteworthy victory of science and winemaking art.

At every step of the process, wine production is a balancing act and even after the wine has been bottled the act continues as compounds in the wine interact with the air entering and leaving the bottle. More often than not this whole series of events goes smoothly, guided by professional vintners, sommeliers, and others. Sometimes things don’t go so well though. Sometimes, the wine is corked.     


A wine cork and a wine bottle opener.
Natural cork can harbor organisms that make wine go bad.


What does it mean if a wine is corked?

A corked wine is one thing you definitely do not want. The name is misleading for some and has been misinterpreted to mean the wine bottle has a cork, as opposed to a screw top, or that there are pieces of cork in the wine. Another misconception is that corked wine will have a cork covered in little white crystals. These are called tartrate crystals and they occur as a byproduct of some wine manufacturing processes, they are perfectly fine. A corked wine is actually a wine that has become contaminated with cork taint.   

Cork taint, unfortunately, is not just a little taste of cork in the wine either. It is a general term used to describe faults in wines which causes them to smell and taste very bad. It is primarily attributed to 2,4,6 – trichloroanisole, or TCA, and 2,4,6 – tribromoansiole, or TBA, which sounds more like compounds used by a Bond villain than chemicals that can ruin a wine. TCA is produced by various fungal strains that can take up residence in natural cork both before and after it has been harvested.

When these natural and airborne fungi come into contact with various chlorophenols, such as what you might find in bleach or other sanitation and sterilization products or the antimicrobial agents used in processing wood, they can then produce TCA. This is produced within the natural cork where the fungi live or it is introduced from the outside and passes through the cork, eventually making its way into the wine.   


What does a corked wine taste and smell like?

Thankfully it is now very likely that you have not encountered a corked wine and if you have, well, you’ve just broadened your wine knowledge. It is often cited that only around 5% of wines with natural corks become corked but the reality might range anywhere from 3% to 8% depending on who you ask. For a wine lover that is 3-8% too much.  

If you do happen to pull the short straw in wine selection and end up with a corked wine here is what you can expect. A moldy basement, a wet newspaper, wet cardboard, and a wet dog. That pretty much sums it up! The aroma of corked wine is often described in these terms and that in itself makes the wine extremely unappealing. It’s important to note that this odor can’t be detected without actually opening the bottle and smelling the wine.

So, sorry to say, you can’t go through the store sniffing every bottle of closed wine to find one that is corked. You also can’t really detect the odor on the cork itself. You just have to smell the wine to know. Your first sniff of the wine will be your most informative though!

Apparently, the human olfactory system adapts very well to the smell of TCA and becomes less responsive to it with more exposure. The more you smell the tainted wine the less you’ll detect the bad odor. The odor itself will also depend on just how strongly the wine is tainted. If the cork taint is minimal you might not even notice at first!   

If you were to be so brave as to actually taste the wine or somehow completely missed its malodor then you are in for another little “treat” with the flavor. If you can imagine a wine with absolutely zero fruit flavor, a wine that is completely flat and dull, you’d be imagining the experience of drinking a corked wine. The smell and the taste combined create a completely off-putting wine-drinking experience.

In some cases, the taste will be your only indication that the wine is corked though. Other elements of a wine, such as oakiness, can completely mask the odor of cork taint and because the olfactory system habituates to TCA so readily an initial whiff can fade quickly. 


A person holding a wine glass at a table outside.
You might finish a glass of corked wine without realizing it is corked.


How can a corked wine be prevented?

Wineries have gone on the full offensive to prevent all sources of cork taint. They have created synthetic corks and screw caps, they have improved quality assurance and quality control methods, they have eliminated cleaning products which might introduce chlorophenols as well as products with tribromophenols, they heat-treat wood to avoid using nasty antimicrobials and some have even brought in dogs.

Yes, man’s best friend is now also wine’s best friend. TN Coopers, a barrel supplier for wine manufacturers, started using dogs for this purpose and now the practice is spreading. Dogs have a nose that is 10,000 to 100,000 times more powerful than a human and this also beats out cork taint detecting technology as well. When these dogs are trained they can detect TCA and other compounds very quickly. This is important at every level of wine production.    

The TCA, TCB, and other compounds that can lead to cork taint don’t only affect individual bottles via the cork. They can also become systemic in winemaking facilities. In addition to cork, TCA can also occur in rubber and bentonite clay (a substance used to purify wine). This means that cork taint can come from many places including the barrels, the hoses, and many other points of passage along the wine production journey.

This creates hundreds, if not thousands, of points for contamination risk. This is where the dogs come in. TN Cooper uses their trained dogs for regular inspections of their own facility and checks all of their barrel shipments just prior to departure. These amazing canines are also contracted by other local members of the wine industry to run sweeps of their cellars and processes. 

Corked wine is a multimillion-dollar affair as it can lead to entire cellars of wine going bad. Being of extreme economic importance in the wine industry preventing cork taint from happening has become the responsibility of people at every level of production. When cork bark is stripped it is tested and some cork manufacturers even submit it to a novel gas chromatography technique that can detect small amounts of TCA in natural corks.

Corks are also subjected to microwave radiation and other methods. The techniques and technologies continue to come and some are hopeful that in the years to come the most common causes of cork taint will be a thing of the past.            


A brown dog's snout.
A dog’s nose might just be the best tool we have for detecting cork taint early.


Can a screw-top wine be corked?

Unfortunately, a screw-top wine is not safe from being corked. The chances of it happening are lower with a screw-top wine though. With bottles that use natural corks both the corks themselves as well as systemic TCA contamination at the point of bottling can lead to cork taint.

A screw-top wine is really just susceptible to contamination at the bottling point. This is not very likely to happen though because manufacturers of screw-top wines are purportedly sticklers for hygiene. Screw caps have their own challenges though. 

Whereas too much oxidation is normally a problem for wine sometimes the opposite is true. Too much reduction, from a lack of oxygen exposure, can arise in wines high in sulfur dioxides. This leaves the wine tasting like rotten eggs if it isn’t balanced by oxidation.

Occasionally sulfur is used as an additive in these wines and a screw cap can make it more difficult for that sulfur to be absorbed into the wine. When this happens that rotten egg taste is only made worse!


How do you know when wine goes bad?

A wine succumbing to cork taint isn’t the only thing that can go wrong with it. There are several ways wine can go bad and each of them manifests differently. You can typically tell a wine is bad from the aroma. An odor of wet cardboard, as with cork taint, vinegar, or heavy raisin are all a bad sign. Taste is another strong indicator a wine might be bad. A very dull fruitless flavor can happen with cork taint while a very sweet red wine (if it isn’t a port or a dessert wine) can indicate a bad wine. 

The sweet red which shouldn’t be sweet usually means the wine has overheated. When that happens it can also result in the cork being pushed out some from the wine expanding in the bottle. Reds and whites which have taken on a brownish hue are also no good, they’ve over oxidized. Wines with astringent chemical flavors are done for too. If you find any of these issues with your bottle you should return it if possible and get another.  


Can you get sick from corked wine?

A corked wine can range in severity from extremely bad-smelling and dull tasting to undetectable. The cork taint is dependent on the concentrations of TCA, TBA, and other compounds in the wine and this is typically at around a few parts per trillion. Something comparable to dissolving a sugar cube in a couple of hundred pools worth of water. Still, the average person might detect the cork taint at around five parts per trillion. At even higher concentrations the only effect will be an unpleasant wine experience. Cork taint will not make you sick. 

Actually, you may have already drunk a few glasses of corked wine in your life and just didn’t realize it. With occasional wine drinkers of the last ten to fifteen years, this is less common. If you are and have been a regular wine drinker, especially throughout the 80s and 90s, then you’ve probably encountered a corked wine. When the concentration of TCA and other negative compounds in the wine is very low and/or the wine has strong overpowering aromas such as oak then it can be very difficult to tell if the wine is corked. Usually, the flavor gives it away, but not always.       

If you happen to have a bottle of slightly corked wine and you think it doesn’t taste or smell too bad then have at it if you want! There won’t be any negative health effects from the cork taint. Still, if you can return the bottle to the store and get another then that is always the best route. 


The inside of a wine store.
Any wine retailer worth their salt will easily make up for a tainted wine.


Can you save a wine that has been corked?

Technically, yes you can, but also, are you sure you want to? For most wines commercially available it is perfectly acceptable to go back to the store you bought the wine in, tell them that it is corked, and they should at the very least give you a new bottle. If they don’t then you should count yourself as a customer lost because that is not good business. 

If the wine is of some greater economic or sentimental value, or you just have a real love for chemistry, then there a few techniques you can try. The upside of cork taint, if you can even call it that, is that the TCA in the wine does not permanently and irreversibly bind to any component of the wine or change its chemistry really. The TCA basically sits suspended in the wine. This means you can extract it. 

The easiest at-home method for doing this was figured out by scientists at UC Davis. All you have to do is pour the tainted wine into a large glass pitcher and then add a sheet of polyethylene (the material used for food wrap or plastic containers) into the mix. Let that soak for up to 15 minutes. During this time it is also important to keep the pitcher covered from the air if possible.

This will help prevent oxidation of the wine which can also ruin the taste. After several minutes you can then pour the wine into another container and it should be drinkable. The way this works is that the molecules of TCA are strongly attracted to the molecules of polyethylene and will stick to them quite strongly.

As the polyethylene soaks in the wine most of the TCA will bind to it so that when you pour the wine out it will contain much less TCA while leaving the rest behind on the plastic. For this to work, it is necessary to use polyethylene specifically so you must check what the material is made of. Cellophane won’t work as well as Saran Wrap for example.   

There are also several commercial purification and filtration technologies available as well as a method that takes advantage of the butterfat in half and half to help chemically separate the TCA from the wine. Companies continue to come up with new techniques for saving wine after it has been affected by cork taint.        


Can you use corked wine for cooking?

This seemingly simple question is not so simple. Some think because a corked wine is still drinkable from a health perspective that means it can also be cooked with. They would be wrong. Cooking with wine is all about flavor and aroma and if your wine tastes like a wet dog then so will your dish. Even a mildly tainted wine should not be used.

You have to remember that, for one, your olfactory system has the unique ability to become accustomed to the odor of TCA. This doesn’t mean it isn’t there though. You might think you have cooked the terrible wet cardboard odor away but someone else might notice it immediately in your dish. The rule of thumb here is to not cook with a tainted wine. Only use normal, properly produced, drinkable wines. 


People cooking over a silver cooking pot.
Try not to cook with any wine that you wouldn’t also happily drink.


Why do wine bottles even have corks?

You might be thinking to yourself, “Hmm, synthetic corks and screw caps have a reduced incidence of being corked right? Why even use natural corks at all?” and that is a good line of thinking. The realities of bottle closure are strongly dictated by the properties of the materials used and their ability to meet the demands of quality winemakers. To date, natural cork still does this the best and most reliably.

One of the biggest reasons for this is that natural cork contains oxygen which diffuses into the wine at a well known and well-understood rate. With screw caps, this doesn’t happen at any appreciable level and with synthetic corks it can occur too quickly. 

Both the rate and amount of oxygen which enters a wine after it has been bottled will determine how well it ages and how good it tastes once it is opened. Most wines are closed with corks for this reason and almost all high-quality wines are cork sealed because of this. Side by side tests consistently find that wines closed with natural corks have better aromas and flavors than those secured with screw caps or synthetic corks. Generally speaking, wines closed with natural cork just age better. 

Due to the importance of oxygenation, it is also important to properly reseal the wine after it has been opened. Cork is very effective for helping the bottle age well but if you want to reseal the bottle for a short time, say at a party, then a wine bottle stopper is in order.     


Final Verdict:

A corked wine is an unfortunate occurrence that is thankfully becoming less and less common. Although some cork taint is nearly undetectable in other cases it can ruin a wine. It is possible to somewhat salvage the wine but why put yourself through that?

A corked wine should simply be returned and replaced. If you or anyone you know thinks they’ve come across a corked wine feel free to give it a whiff and a taste, you might quickly realize what a thing of beauty a well-made wine really is.    

Bonus tip: While you’re at it, check out this video on how one winemaker decided to solve their cork taint issue!



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