Most of the time when we don't like a wine, it is just a question of taste. It simply is not to our liking. Occasionally, but not as rarely as one may hope, the problem is not of preference, but of fault. Almost any wine fault will be viewed by someone or another as either not too bad, or even as a positive trait. This has to do with how pronounced the fault is, and the individual's ability to perceive the fault. So even with faulty wines there may not always be agreement.

In the ages before Pasteur discovered the mechanism of how grape juice turns to wine, faults were common. The addition of fruit juices or even pine sap were ancient remedies for hiding the off flavors. The modern Sangria and Retsina wines of today owe their existence to these practices.

Even as recently as my earliest forays into wine, it was not uncommon for bottle variation to be so great that few examples in any given case would taste the same. The last thirty years have greatly changed this for the more commercial strata of wines, although some of the more hand crafted, so called "natural" wines that are gaining in popularity may still share this level of unpredictability.

Here are some of the most common faults you are likely to come across, so you can recognize them when you encounter them, and in a few case even overcome them.

Corked Wines

This is the most famous of wine faults, and one that is so persistent it has brought a whole new way of sealing bottles to the fore. A corked wine will smell musty, like wet cardboard. If you encounter this, and it is practical, open a second bottle of the same wine (if you are in a restaurant and find this problem, the staff should not hesitate to open another bottle for you). If the odor is only in one of the bottles, chances are that it was indeed "corked". If the smell persist in the second bottle, then it may be a mold issue, often from the barrels, and the vintage from the producer may be one you wish to avoid.

Corked wines contain a taint referred to as TCA (short for a long chemical name). It gets it through bacteria that manages to survive the bleaching process of the corks. It can also get into wine through equipment or tanks in a winery that have been similarly cleaned with bleach. Some water supplies are also tainted with TCA and you may encounter the smell not only in wine but on the surface of something recently cleaned. There is not much you can do to fix this problem, except open another bottle.

Sour / Vinegar

This was historically one of the most common wine problems, but now it is relatively rare. It is still the one at people think of the most. I am often asked if an older, unopened bottle of wine might have turned to vinegar. The answer is actually, that this is unlikely. For a wine to turn to vinegar it has to have a specific (acetic) bacteria infection. All wine tends to have a touch of this and it is referred to as Volatile Acidity (VA) and a little is good, as it allows the aromas of the wine to expand, too much is bad. How much is too much depends on the person.

Beyond VA a wine only really turns to or approaches vinegar if it has been exposed to the air. A bottle once opened will start to sour. How long before the wine is unpleasant depends often on the wine, and the person drinking it, but usually takes at least over night. Putting an open bottle in the refrigerator can slow down the process, as can removing the air with a hand pump or adding a more inert gas. There are any number of devices on the market that work on these principles.

Oxidation

In the wine world we have a special word for a wine that has been exposed to oxygen: Maderized. It is a reference to Madeira wines which are made purposely with exposure to to oxygen and heat. Like Madeira a maderized wine will often be a shade of brown and taste more or less of hazelnuts. This is a common fault with older wines or ones that have been stored badly. There is nothing that can be done to redeem a wine once it has maderized.

The mechanism involved is exactly the same as why an apple browns after you slice or bite into it. Antioxidants, which seem to be the cure all for aging and other ills of late, can slow this process down, and indeed wine has many antioxidants which is why it does maderize any more quickly than it does.

Rubber

There is an off aroma that many have equated with the smell of a rubber shower cap or boots. If it is stronger it may even remind you of the smell of squealing tires. This aroma is technically due to a group of chemicals called Mercaptans or Thiols (mercaptans are more commonly used in wine speak, thiols in organic chemistry). The wine ends up with this smell due to a problem during wine making, usually related to not enough oxygen at the right time. Interestingly enough this is one that you can cure (temporarily) or test for in your home. All you need is a bit of copper (in the US a penny will work). Simply dipping the copper into the wine will make the smell go away immediately.

Sadly, I have found this fault to be one of the most common that I encounter in modern wines. Many professionals seem to be less sensitive or more tolerant to it, and so it has become much more pervasive that I would wish. The copper trick works at the point of production too, and for years winemakers have used a bit of copper to correct the problem. Recent studies show that the copper probably only hides the aroma, and that it may come back in the bottle with time. This may explain why the fault gets in so many released wines. While copper may make the wine easier for you to enjoy now, it is really up to the winemaker to be more to careful to avoid the problem in the fist place.

Sulfur

Related to the rubber / mercaptan issue I relate above, are other sulfur aromas. The worst of these is hydrogen sulfide, the rotten egg smell. Uncommon in wine, but not unheard of, it can really make a wine nasty.

More common and less nasty is the general "burnt match" aroma of sulfur itself. I will avoid a long discussion of bonded versus unbounded sulfur and the difference between sulfur and sulfites, and their potential for health issues and or headaches. Suffice it to say that you should no more experience the aroma of sulfur in wine that you should notice any preservative in any food.

Decanting with some force, a wine with sulfur aromas will usually make them go away in an hour or less.

Wet Leaf Aroma

This, especially when combined with a bit of unexpected sparkle to the wine is usually due to the secondary fermentation - the malolactic fermentation - happening in the bottle. It is a case of sloppy winemaking and is not common, but I have run across in now and then. It is a good reason to reject the wine in a restaurant, but at home you may want to try the forcible decanting trick.

Overwhelming Vegetation Aroma

Sauvignon Blanc is noted for its grassy aroma, other wines shouldn't be. While rare this can actually be due to a ladybugs that end up with the grapes at harvest. The taint is called pyrazine and most people won't ever run across it. I am primarily including it here because the 2011 vintage of Burgundy has been pegged with this fault.

Barnyard Aroma

Another of the more common off aromas in wine. How much this one bothers you depends on your sensitivity to it. It is most common in Old World wines, especially those of St. Emilion in France where if it is not too pronounced it is lauded as giving the wine character. It is specifically referred to as Brett, short for Brettanomyces a genus of yeast.

There are a lot of different strains, and some are nastier than others, but most end up in the wine because the winery is contaminated with it. This is why it is so common in St. Emilion, due to the famous limestone caves have harbored the yeast for centuries.

There is nothing you can do about a wine that has this aroma, but it is important to know that if you find it in a young wine, the same wine will show it more strongly when it ages, and that all wines from that producer will almost certainly exhibit some signs of Brett.

Others

There are any number of other off aromas, and for those that are interested one source is my website http://www.wineeducation.com/faults.html. There are also kits you can buy that have examples of the aromas so that you may better train yourself to identify them. I recommend these for serious wine professionals.

So the next time a wine seems off to you, know that it may not just be you, the wine itself may have a fault. Being able to identify what is wrong with the wine may help you determine if you should avoid the wine or even the producer in the future. Here then is to wishing that all of your wines are to your taste, and none dirtier than you like.