If you’re someone who regularly eats out and orders wine with their meal, you’re no doubt familiar with the practice of tasting the wine before it is served to the table. The idea, of course, is that one chosen person tests to make sure the wine isn’t corked or doesn’t contain any other fault.

Yet how many of us can honestly say that we could recognize a faulty wine or would be able to confidently return a bottle to a wine shop after discovering a flaw?

Most people know or have heard of the term "corked" but in actuality, corked wines account for as little as 5% of the production of wines annually. There are various other lesser known flaws and faults that can affect wines, and yet, the presence of a flaw does not always mean that a wine can’t be served. Here we’re going to look at the most common flaws and faults, how to recognize them, and ultimately, whether or not it is a problem that can be rectified.

Oxidized Wine

When we use the term oxidized, what we mean to say is that it has been exposed to an exceptional amount of oxygen. This can happen because of a faulty cork or stelvin cap that let in too much air, or because the the bottle has been opened and left for too long without being finished (roughly overnight/one day outside the fridge and a few days inside it).

An oxidized wine can be recognized by a loss of intensity in aroma, color and flavor; these deteriorate, becoming much more acidic - no doubt you may have tried a wine which you thought tasted like vinegar, this is oxidation.

In white wines, look out particularly for notes of rotten green apples. In reds, you’re looking more for overly matured dried fruits or vegetables, think very dark, acidic sun dried tomatoes.

Oxidized wines can not be fixed, it is an irreversible reaction. If you bought the wine at a store, or ordered it in a restaurant, do not hesitate to send it back, the flaw is coming directly from a faulty cork or bad storage. We've covered sending back a faulty wine in What Does Corked Mean and other Tricky Wine Terminology by our resident sommelier, Christie Kiley. Sending back a faulty wine usually isn't an issue, as no reputable merchant or restauranteur is oblivious to the possibilities of a tainted wine.

If, however, the effects of oxidation are very subtle and have come directly from too much exposure to air, the wine can still be drunk. It should be noted, though, that the wine has now significantly decreased in quality, and what you’re drinking is not an accurate representation of what the winemaker or vintner intended.

Sulfur Compounds Can Cause Wine Taint

Nearly all wine bottles these days will display somewhere on the label the words "Contains Sulfites". This is normal, because sulfites are used for preservation in the winemaking process. Even organic wines, in which the producer is aiming to add as little artificial or unnecessary compounds as possible to the wine, contain sulfites, because they occur naturally, albeit in very small doses. There are, however, naturally occurring sulfur compounds which present themselves as flaws, some of which can be rectified while others can't.

Sulfur Dioxide (SO2)

Sulfur dioxide is a chemical preservative added during the winemaking process, present as an odor of burnt matchsticks or rubber. Intensity reduces with oxidation either via decanting the wine or swirling it in its glass. Wine can still be served with this type of fault.

Hydrogen Sulfide (H2S)

Hydrogen sulfide smells like hard boiled (and sometimes rotten) eggs or rubber. This compound forms when absolutely no oxygen is entering the wine bottle during storage. Otherwise know as reductive odors, this fault can be solved via decanting, swirling and giving the wine time to breathe. There are instances when reductive odors are just too strong and wine can not be fixed.

Mercaptans

The mercaptan flaw can be recognized by a smell of rotten onions, boiled cabbage or cauliflower. It is unfixable and wine should be returned and replaced.

Brett (Brettanomyces)

Brettanomyces or Brett is a wild yeast, which when present in wine, adds a smoky or "animal" character to the bouquet. For years, it has been argued whether it is a flaw or whether it actually improves certain wines. It is much more common in red wines which have lower acidity, and in character, it is similar to the effects of evolution/aging. Too much brett in a wine causes a smell that is described as like a stable or a sweaty saddle - definitely not desirable.

Brett is more common in Old World wines and indeed is generally more tolerated by people living in old world wine regions.

Corked Wines (TCA)

Trichloroanisole (TCA) is the chemical which is responsible for producing what we know as "corked" wines. The chemical can initially be found on certain tainted corks before being transferred to the wine.

Corked wines are recognized by their musty character - think wet dog, damp room or old books. This musty character overpowers any of the fruity aromas or flavors present in the wine, and corked wines should never be served.

Wine producers always want to know about potentially contaminated wines so they can recall faulty batches before receiving a bad reputation. Sommeliers and wine sellers normally take it upon themselves to inform wineries if they come across a contaminated batch of a particular wine.