Last night we opened a bottle of Bordeaux red to go with our evening meal. The wine was ever so slightly corked, meaning that the wine is "contaminated " with either the chemical 2,4,6,trichloroanisole (TCA) or 2,4,6-tribromoanisole (TBA). These two chemicals can ruin the taste of wine by rendering it with the earthy smell of a damp cellar and a taste of damp rotten cardboard. The TCA usually ingresses into the wine through the cork. A cork can be infected with fungal spores which convert chloro-phenolic compounds, used in the winery, to TCA or less commonly to TBA: hence the term corked wine.
Humans are able to taste TCA at levels of parts per trillion; some humans are more sensitive than others. My wife is more sensitive to the smell than me. She is able to smell cork taint from across the table when the cork is pulled. Sometimes I can smell the cork taint on the cork after pulling.
On this particular evening my wife did not smell the cork taint and I did not smell a cork taint until I swirled the glass before drinking it, for some reason my wife did not do this.
This particular wine was not completely ruined by the cork taint and I could taste plenty of fruit in the wine. It was clear that the wine was contaminated at a very low level. Some people, such as my brother-in-law, cannot sense low levels of cork taint, so he would have found the wine perfectly acceptable.
When you are in a restaurant it is best to swirl your wine before you agree that it smells acceptable. The swirling will release the flavour of cork taint. A good wine waiter should smell the cork before serving you the wine to taste. However, in the case of this wine there was no smell off wine taint on the cork, and my wife can confirm this. It would be embarrassing to send back a bottle of wine if you have not been able to smell or taste it has been corked before slugging it back.
It would be unfair to name the wine as we drank another bottle of the the same wine and its 2015 vintage. The wine was perfectly acceptable, in fact it was very good wine and very good value for money.
The cork taint is not just confined to reactions of the cork. It can ingress into to wine from similar chemical transactions when fungal spores in the atmosphere meet choro-phenolic compounds used as sterilising agents for rubber hoses or seals. This is termed systematic contamination. TCA can also be produced when wooden pallets are exposed to fungal spores in the vineyard or transportation. The TCA is then able to penetrate a natural cork to contaminate the wine. It is quite possible that TCA could contaminate a wine that is sealed by a plastic cork or screw cap, I have never experienced this, however.
Any wine sealed with a natural cork could become corked despite the price of the wine. If you open a bottle of wine that is corked you can return it to the supermarket or wine merchant for a refund, You must do this quickly, however. Our wine was bought in France so it is not worth the time and effort to go back for a refund.
Some wine experts claim that you can remove the cork taint by dipping some cling film into the wine and stirring it for some seconds; apparently the polyurethane is able to absorb the TCA or TBA and remove it from the wine.
I have tried this before but it didn't work. I am going to try this again as the TCA is present at very low levels: more of this later.
Modern winery techniques are reducing the incidence of corked wines sealed with natural corks. I like the idea of natural corks produced from oak trees in Portugal. Natural corks are the best method of sealing wines which need to be kept to improve in the bottle over a number of years. They allow oxygen to permeate into the wine in exceptionally small quantities to help age the wines and break down tannin. Of course, too much oxygen will eventually ruin a wine, but some wines can age for 50 years or more, in a cold and dark cellar, to improve the taste.
The use of natural corks also helps with the sustainability of oak forests which cannot be a bad thing.
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