Wine flaws are not necessarily the result of bad winemaking. Wines can be defective if they have been improperly handled or stored. That said, the presence of a wine flaw or defect does not automatically make the wine bad and worthy of cooking. The key is knowing how much is too much.
Certain characteristics that make a wine flawed can actually, in small amounts, be considered by some people to be a plus. It's similar to adding garlic to food: A little bit enhances the dish, but too much ruins it. Here are common culprits behind most wine faults.
Your wine smells of damp cardboard or musty basement. Whether the odor is pronounced or just slightly dank, it came from a cork tainted with a chemical compound called TCA. When the wine is damaged in this way, it's said to be corked. By industry estimates, 3 to 5 percent of all wines are corked. Cork processing improvements have been made to eliminate TCA, but many wineries are so fed up they are resorting to closures such as screw tops as permanent remedies. Very rarely does cork taint enhance a wine, even in small doses.
The wine tastes dull, cooked, or a little sherry-like. A white wine has an off color — brownish or very dark yellow. These are all indications that the wine has been exposed to excessive oxygen.
It could have happened while the wine was being made or when it was being stored. If wines are stored upright for long periods instead of on their sides, the cork can dry out and let air into the bottle.
Perhaps your wine smells like vinegar or nail polish remover. This is an extreme case traceable to a bacterium called acetobacter and oxygen. Acetobacter is everywhere — on grape skins, winery walls, barrels. By itself, it has no aroma or flavor, but when it meets oxygen in winemaking, it first produces the compound ethyl acetate (nail polish remover) before completely reducing the wine to acetic acid (the vinegar aroma).
The term “volatile acidity” (VA) accounts for these two conditions, although once a wine reaches the level of acetic acid, it's considered oxidized. Many wine connoisseurs enjoy low levels of ethyl acetate.
Many people assume that when a wine gets too old, it turns to vinegar. More likely, it will become dull and take on a nutty taste. Thanks to Louis Pasteur and his groundbreaking work on fermentation, winemakers learned to keep wines out of contact with air and bacteria during the production process. Unless something goes terribly wrong with the cork, oxidation is rarely the winemaker's fault.
Your wine smells like a barnyard. It may be the result of a yeast called brettanomyces — brett, for short. Brett grows on grapes and in wineries and is difficult to eradicate. Winemakers use special filters to help reduce its growth. Some wine drinkers enjoy a low level of brett, maintaining that it adds complexity to the wine's aroma, but too much completely spoils the wine.
Your wine smells like a struck match. Winemakers add sulfur dioxide to preserve the wine, but in excess it ruins the wine. Cheap white wines are most likely to have sulfur problems.
The wine is brown, and it smells like it's been cooked. In Madeira, this is a plus and part of the wine's essential character. Elsewhere, it's a flaw, and the term “maderized” will be used. The wine has likely experienced severe fluctuations of temperature in a short period of time or been stored in extreme heat. If the cork is protruding slightly from an unopened bottle, the wine could be maderized.
Personal preferences don't reflect a failure in the winemaking process, but if you don't like oak in wine, you will probably consider that rich California Chardonnay to be flawed. Other wine drinkers cannot tolerate acidity, meaning that such a person will push an otherwise flawless dry Riesling away from his plate.