Trust your first impression! The initial sensation is always right.
The problem of cork taint has been occupying winemakers for over a century.
According to estimates, as much as 12% of bottles produced and 5% of wines sealed with a cork stopper may be affected. It is not foreseeable or avoidable – such as by keeping the bottles upright instead of laying them down.
The underlying cause is an organic compound in the cork – called trichloroanisole (TCA), a molecule made of carbon, hydrogen, chlorine and oxygen – which derives from moulds or fungi developed by the plant from which the material was extracted. Even if the wine is not in direct contact with the cork, the odor contaminates it anyway.
The cause might not even be the cork but the barrel, the bottling equipment or the wood used to keep the wine in the cellar.
If the cork smells of wine, great. But if it has that particular odor like mould or a damp cellar, then the bottle will be replaced with one that, hopefully, is free of that problem.
It is like the smell of a damp towel left for days in the washing machine, of mushrooms, wet earth or sodden cardboard. Even if there is only a slight cork taint, you will still notice a bad smell of mould.
In exceptional cases, especially with white wines, the defect may manifest as a lack of aroma, without the specific odor of cork.
If your nose cannot tell that the wine is not good, then your palate will. A corked wine tastes as bitter and horrible as the odors we mentioned earlier. If you have the misfortune to experience it, rinse your mouth with water and change glass. Don’t use the same glass for the next wine.
Screw tops may help to protect the wine – as long as the contamination does not happen in the barrel, in which case you have reason not to trust the producer’s quality control procedures.
TCA can also be found in tea and drinking water: it is not hazardous to health in small quantities, although it certainly spoils the experience of tasting a wine.
A wine that tastes of cork can be mulled safely, because the TCA will simply evaporate when heat.
Of course, each situation must be assessed on its merits.