What does a ‘corked’ wine mean?

A wine being ‘corked’ is not a consequence of time under cork or having bits of cork floating in it, but a specific chemical (2,4,6-trichloroanisole, or TCA). This taints the wine, which it acquires through contact with a naturally occurring mold in the bark of the tree from which the cork is cut. (Technically – as the cork industry is very keen to point out – it can come from any wood with which the wine has been in contact, and indeed, affected barrels are occasionally discarded/treated, but such wines should not reach the bottling line.)

A wine is – or hopefully isn’t – corked the moment the cork goes in (after a few days anyway). And it stays that way. The TCA smell is of moldy cardboard and worsens with oxygen (i.e., once opened). The dank smell that very old wine can acquire through transpiration is similar smelling (actually likely another type of anisole) but different in that it can dissipate once the bottle is opened and does not suppress the fruit aromas/flavours.

TCA is one of the most pernicious aroma compounds known to man. Humans can detect it at concentrations as low as 1-3 PPT. Parts per trillion is difficult to measure (1 PPT is 1 second in 320 centuries, one drop in an Olympic swimming pool – pretty much homeopathic!). Everyone can smell TCA at around 30 PPT. At the lowest concentrations, it simply dulls the fruit and makes the wine seem flat and boring. At higher levels, the wet cardboard smell is unmistakable. But something ’corked’ to one person may not appear so to another.

The good news is that the better and more expensive the wine, the more the producer will have spent on the cork, and the less likely the problem is to develop nowadays.

More good news is that TCA is harmless and has quite a low boiling point, meaning that you can use affected wine for cooking, and the smell will likely disappear. (Alas, pasteurisation does not cure cork taint, as it ruins the wine in different ways.)

However, all corks have a lifespan, eventually losing their elasticity, thereby making a less perfect seal and allowing too much oxygen (and possibly worse) in. Eventually, they may dry out and crumble completely. The best wines use not just the best but also the longest corks for this reason.

When a wine gets to about 50 years old, it’s probably time either to drink it or have it (professionally) recorked (which the original château will usually do – for a price, but including topping up if the level has gone down too much.)

There have been some fairly recent positive developments. About 30 years ago, it was estimated that about one in ten bottles of wine was TCA affected. Few industries would tolerate a failure rate of 10% when there are valid alternative solutions. The first solution was the plastic cork. These can be hard to get out – and even harder to get back in, should you want to. Plastic simply does not have the enduring elasticity of natural cork.

Then came screw caps, whose only real ‘problem’, as a closure for wine, is image. Any wine destined to be consumed within about three years would be better for using a screw cap. The only thing to be gained from cork is that after more time than this, the
natural transpiration of the oxygen, both within and externally to the cork, will allow the wine to gently oxidise without risk of bacterial or other spoilage. (Some modern screwcaps can also do this, in fact).

For the same reason, such a wine will benefit from decanting, swirling in the glass, and opening ahead of time. However, none of this applies to pretty much all rosé and most whites, especially those that have not seen oak in their production. These suffer – rather than benefit – from oxidation. As do many reds, particularly those low in tannin and designed or destined to be drunk in youth.

However, screw caps do have an image problem (ranging from no issue in New Zealand, almost none in Australia and Scandinavia, to changing perception and acceptance in the UK, and up to practically no current acceptance in the USA, Italy, and France – for all but
the very cheapest wines, anyway.) Other alternative closures, such as premium glass stoppers or mass-market Tetra-Pak, can achieve the same result but may have similar or other image issues.

The cork industry has acknowledged the problem, and today, sterilisation is much more successful and less batch-led (remember, one part per trillion is enough, so as soon as a tank of cleaning water was contaminated, so then would everything that came into contact with it subsequently.)


The incidence of TCA contamination in wine has now gone down to less than 2%. The only affected corks are those where the mold was actually growing in that precise place in the bark in the first place, rather than anything that has come into contact with the same chlorine-based sterilisation (bleach) solution. Speaking of which, the ‘chloro-’ in TCA is a legacy of chlorine. If the corks are sterilised with ozone rather than bleach (much more expensive, as anyone who has switched a swimming pool from chlorine to ozone can attest), TCA cannot develop, even if the mold is there. Some cork companies have also developed patented methods that use Carbon Dioxide instead.

Top California producers sometimes soak test – each cork is placed in a saucer of water overnight, and then a person smells the water in the morning, discarding any affected corks. This costs about $1 per cork, which is expensive but may well be a price worth paying for a wine that may sell for $100 or more.


It is not only wine that gets contaminated with TCA (it is not only cork oak where the mold exists). Bananas and root vegetables (carrots especially) seem susceptible to the taint, especially if pre-prepared (i.e., sold in plastic bags or as part of a mixture). Even
mineral water in plastic bottles can carry the taint. As before, though, it is harmless and not likely to survive cooking.

The better the quality, the less likely problems are to develop. Drinking better quality is better for your health in every way.

Santé!

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