Smellable faults

Some wines smell so stale and unpleasant that the taster is unwilling even to taste them. The most likely explanation for this is a mouldy cork causing cork taint. Such a wine is said to be corked, but a wine served with small pieces of cork floating in it indicates a fault in the service of the wine rather than a fault in the wine. Contact with fragments of sound cork does not harm wine.

Other off-odours can vary considerably. Oxidized wines (see above) smell flat and aldehydic. vinegary wines indicate the presence of acetic acid due to microbiological activity by bacteria and yeast. ethyl acetate, hydrogen sulfide, mercaptans, excess sulfur dioxide, and the smellable compounds generated by some bacteria can all be reasons for judging a wine faulty. (See also reduction.) The picture is complicated, however, by the fact that we all vary in our sensitivities to most of these compounds (see tasting and ladybug taint), and some of them may be more acceptable in some sorts of wine than others. Acetaldehyde, for example, is the principal odorant of fino sherries, but definitely indicates over-oxidation in white wines, and makes red wines taste vapid and flat. Although the average palate should not detect acetic acid on a fault-free wine, there are some much-admired, full-bodied red wines (such as some port, penfolds Grange, and vega sicilia) whose volatility is much higher than the norm. Many fine German winemakers at one time deliberately used relatively high concentrations of sulfur dioxide to preserve some of their best wines for a long life in bottle.