Sniffing out wine faults

corkWith careful consideration you choose a beautiful bottle from your cellar and pour a glass, only to be greeted by a horrible smell or strange taste. Hell and damnation, what just happened?

When it comes to wine faults, we won’t attempt to discuss all of the possibilities – even a book won’t be enough! Especially considering that the very notion of a “fault” is debatable. For some, a powerfully oaky smell is considered a fault, while it is a sign of quality to others. Similarly, the presence of volatile acidity (VA) might upset the purists and excite the fans of natural wine.

We don’t suggest that the problems associated with an imbalance of natural components – such as bitterness or acidity – are not faults, but our aim is simply to list the most common wine faults. While smell and taste is frequently related, a wine can sometimes have a fault on the nose, with an unaffected palate…

Let’s start with our favourite enemy, cork taint! The cork closure is often directly or indirectly responsible for this common fault, resulting in a pronounced musty smell of damp earth, rotten wood or dust. This makes it the easiest to identify – if you detect an overpowering whiff of mouldy cork, it’s a great wine down the drain! While cork taint may originate from the cork itself, it forms as a result of a chemical process involving the trichloroanisole (TCA) molecule, which can also be present in treated wood (eg. wooden beams or pallets).

An infected cork can additionally cause faults other than cork taint. When slightly defective, it can simply make the wine dry or taste a bit flat. It may be difficult to identify if you aren’t familiar with the specific wine, but it is hard to miss if it affects a bottle that you regularly taste.

The second most encountered wine fault is probably reduction. In this case you will perceive aromas of old cloth, mercaptans or gamy flavours, in varietal wines such as Syrah, notes of tire or rubber. Note that reduction doesn’t affect the taste of the wine. This fault could occur if a wine was closed too tightly during its development, depriving it of oxygen. While these flavours can be very aggressive and unpleasant, it normally disappears after the wine spent some time in contact with air. If it persists, however, then it is more likely a fault imposed by the wine closure.

One can also come across a wine with the opposite fault, namely oxidation. Like all ‘living’ things, wine naturally oxidises in the air. Even in your glass, it does so very slowly, generally improving the wine’s expression. Sometimes a wine can be kept open for a few days before it starts to develop some oxidised notes. However, if the wine is already oxidised at the time of opening the bottle, then it is faulty.

An oxidised wine has notes of overripe apple, cider and nuts. On the palate, oxidation results in a flat and stale wine, adding some stewed fruit flavours. Oxidation is an irreversible defect, which will worsen even more when the wine comes in contact with air. However, some wines have a deliberate oxidative character, like vin jaune (yellow wine) or Château-Chalon of the Jura, Spanish Jerez or older Rivesaltes or Banyuls from Roussillon. Then, miraculously, this ‘defect’ becomes an amiable trait! Wine can sometimes be so complicated…

The next fault is a fairly widespread one, caused by phenolic characters (notes of horse stables, plaster and wet dog). This is usually the result of unwanted yeasts starting to ferment, specifically brettanomyces. The presence of brettanomyces is often linked to poor winery hygiene.

Lastly, we look at the smells and tastes caused by faulty viticulture or winemaking, for example insufficient ripeness or excessive additions (sulphur, aromatic yeasts, etc.). If you detect aromas of geranium, dried ivy leaves, cat’s pee (for Sauvignon) or green peppers (for Cabernet) – coupled with an assault of harsh, ‘green’ acidity – it is almost a sure sign that the wine was produced from under ripe grapes.

For sulphur (aside from the headache), be on the look-out for notes reminiscent of a drawn match. The wine will also seem tight on the palate, with its aromatic expression restrained.

Finally, if you note very pungent chemical smells of candy and banana, you are most probably in the presence of wine made using artificial aromatic yeasts. The winemaker might think that the fragrance is appealing – or perhaps he was made to believe this by his consultant or supplier – but this is more a case of being gullible, than an actual wine fault!

In the end, to conclude this quick overview of wine faults, it is important to remember that it all depends on the level of perception and sensitivity to each compound, varying enormously among tasters. For example, we are not equally perceptive to bitterness or acidity. The process of wine tasting should therefore remain a school of humility and tasters should be open to diverse opinions. Granted, the horrible taste of cork taint will be horrible to everyone!

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Other things to read on the iDealwine blog:

Understanding sulphites in wine

How to store an opened bottle

Why is it Château in Bordeaux and Domaine in Burgundy 


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