Although modern technology has wiped out many of the wine fault problems of the past, the modern consumer should still be aware of possible defects that can ruin any bottle of wine. One of the oldest and most common problems with wine surprisingly involves the cork. Corked wine is wine which has been sealed with a cork contaminated with cork mold. Although certain light levels of corkiness can remain undetected even by professional tasters, corkiness is widely considered a fatal flaw which ruins the flavor and aromas in the wine. Heavy corkiness is easily detectable by the mildewy, damp cardboard like smell and flavor it imparts to the wine. Although the problem is not as grave as it used to be and producers are coming up with new ways to prevent it, about 4 percent of wines still become corked.
Another fault that wine can develop, although a less common one, is known as oxidization. Oxidized wines have been exposed to air for a greater period of time than desirable. Although some oxidization is necessary to develop a mature and aged wine, oxidized wines develop a sour apple taste and a brown coloring. Oxidization can occur when a faulty cork allows air into the bottle or when air reacts more quickly than usual with the wine after the bottle is opened.
Vinegary wine is another fault that can develop from an overabundance of the bacteria that make vinegar are present in the wine. Although very small amounts can be used in some wines, this defect causes a piercingly irritating smell and taste. In the past, vinegary wine has a sign of bad quality but has become less and less a problem for todays wines.
Making a good bottle of wine becomes more than just a matter of good grapes when considering all the things that can go wrong. Other wine defects include an infection of Brettanomyces or "Brett," a wild yeast that gives wine a leathery, metallic aroma and flavor. In small amounts, Brett is considered by some as a characteristic of complex and rich aged red Burgundies, Rhones, Bordeaux and Italian wines. Sometimes, Brett infections are a result of bad sanitary conditions in a winery. Other defects, such as marcaptan, evolve during the fermentation process and produce a putrid odor that makes the wine completely unsuitable for drinking. Too much sulfur dioxide in a wine produces a burnt smell and stinging aftertaste. Although some sulfur is used in the winemaking process as a sterilizing agent and antioxidant, many people are allergic to sulfur. On top of the added sulfur, some sulfur is also produced during fermentation. Technology is working to eliminate the need for the added sulfur and allow more people the chance to enjoy wine.