A corked wine has a distinctive, musty smell. It's the smell of a chemical compound called 2-4-6 trichloro-anisole (TCA for short - remember that one for your next dinner party), which is sometimes formed within a cork by moulds. It's not the actual smell of the moulds themselves.
It's a fast mover, as smells go, and it quickly dissolves in the wine. Different people vary in their sensitivity to TCA. Even amongst professionals, some can detect the merest trace, whilst others fail to notice a serious contamination. Statistically, one bottle in 20 is likely to be corked to some extent. Of course, the problem only affects natural corks, not the new plastic ones: thats why plastic corks are becoming so popular. TCA won't harm you, but it spoils the wine.
When there's barely enough TCA in the bottle to recognise the distinctive smell, it makes a wine taste flat, less fruity, less interesting. At higher concentrations, you get the musty smell and taste. The smell intensifies after the wine has been poured for a moment or two. The cork will smell musty, too. The blame usually lies with the cork producer rather than the winemaker or retailer.'Corked' refers only to the smell and taste, not to a wine that has bits of broken cork floating in it. If you think a wine is corked, re-cork it with its own cork, and return it. You can use corked wine for cooking - boiling will drive off the nasty smell.
An oxidised wine (sometimes referred to as a 'madeurised' wine) has been attacked by oxygen to the point of tasting dull, fruitless or even rather like a bad sherry.
White as well as red wines take on orange then brown colour as they oxidise. A wine may be oxidised because of lack of care in the winemaking or bottling. Its cork may have dried out and let in air, especially if it was stored for too long upright.
You or the retailer may have kept it too long - most whites and inexpensive reds are made for quick drinking, and will oxidise within a year or two or three. Sunlight or bright shop lighting can speed oxidation, and so can heat. Recent purchases that taste oxidised when first opened should be returned. But it's not the retailer's fault if you have kept a cheaper wine at home for months, or an expensive wine for too many years; and it is perfectly normal, indeed inevitable, that an opened, unfinished bottle will oxidise within a day to a week, depending on the wine. You can use up oxidised wine for cooking - it won't spoil the flavour so long as it's boiled.
Acetic wines smell and taste vinegary. Professionals often call such wines 'volatile' and talk of 'volatile acidity' - acetic acid.
Wines contain various natural acids, all of which taste more or less sharp. Without them, all wines would taste dull and unappetising. Some perfectly sound wines taste quite sharp or tart - well made Vinho Verde or Muscadet, for example.
A tiny bit of acetic acid is allowed in wine, and can even add an attractive element to a wine's flavour. But when present in excess, when you can taste and smell something that really reminds you of vinegar, it becomes a fault.
Acetic acid is formed by yeast and bacteria. If a newly opened bottle tastes acetic, return it. However, it is perfectly normal for an opened and unfinished bottle to become acetic - this may happen within a day to a week or more, depending on the wine.
Acetic wine can be used up in stews, casseroles, coq au vin etc, anything that is boiled for quite a long time. The acetic acid will have boiled away by the time the dish is finished.
Like many other food and drink producers, winemakers use sulphites as a preservative, to protect against micro organisms and oxygen. Winemakers add sulphites to wines throughout the winemaking process, topping up the sulphite level at bottling time. Without sulphites, wines would be attacked by all kinds of micro organisms, as well as oxygen from the air. Even organic producers use sulphites, and their rules permit it.
Good winemakers nowadays use far less than they used to, because they properly understandthe doses required to do the job. But if the wine making is careless, or the winemaker clueless, extra sulphites might be added to compensate for bad hygiene, bad cellar work, or for extra protection for the wine, just in case.
Such wines smell like struck matches, dull, slightly smoky-dirty, and catch at the back of your throat and make you cough. Very recently bottled wines sometimes taste of sulphites because the sulphides added at bottling time have not yet been fully incorporated into the wine. This may be a phase and may pass, leaving the wine tasting clean and fresh after a week or two. If a wine tastes unpleasantly of sulphites, take it back. To most people, sulphites are harmless but some asthmatics can be seriously affected.
Sulphide compounds (as opposed to the sulphites used in wine as a preservative) come in a range of revolting flavours: hot water bottles, rotten eggs, blocked drains, sweaty socks. These might be formed by yeast or for other reasons during the winemaking, or in the wine in bottle. Champagne is particularly prone to develop sulphidic smells if the bottle is exposed too long to light.
You can return bottles of sulphidic wine. But you can also cure it yourself!
If a still (as opposed to sparkling) wine smells of hot water bottles, rotten eggs or whatever, try tipping it roughly into a jug, then into another jug, and back and forth a few times until the smell has gone. Or more peacefully drop a washed 2p coin into your wine glass and swirl it around a bit. The copper reacts with the sulphide, and makes the wine much less pongy.
Crystals in the bottle are a good sign. In white wines you may occasionally find little clear glass-like shards or crystals. They are not glass, but tartrate salts, formed in the bottle from natural grape components. The winemaker could have treated the wine to ensure that no crystals would appear after bottling. But the treatment can remove a little of the wine's flavour along with the crystals, and some good producers prefer not to treat. In red wines, the crystals get mixed up with colour and tannins from the wine. The resulting deposit may be fine and powder-like, or crunchily crystalline.
You're more likely to find crystals or deposits in finer, older, mature wines, including vintage port, mature red Bordeaux or Rhone wines, or mature Rieslings from Germany or Alsace.
You may need to decant a wine with a deposit to avoid clouding the whole bottle, or serving crunchy dregs.
Floating pieces of cork in a wine simply need fishing out. Usually the corkscrew (or its owner) was the culprit! Poor corks, with too many 'veins' are more likely to crumble, and more liable to harbour 'corked' flavours, or let in air to oxidise the wine. Dried-out corks also let in air and bacteria, making the wine acetic and/or oxidised. So scrutinise a wine with floating cork bits with a little more suspicion than usual, but the chances are there's nothing wrong.
