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Waiter, There’s a Flaw in My Wine
Spotting Common Wine Faults
It’s happened to every wine lover at one time or another.
You are sitting down to a wonderfully prepared dinner, having opened a well-chosen bottle of wine.
Spanish Rioja bottles. Spanish Rioja bottles.
You breathe in the intoxicating bouquet and — pee-yew! The stuff smells like a damp basement.

In the production of wine, there are many things that can go wrong. First are flaws that are considered subjective. These flaws differ from person to person. One person might consider a wine too sweet, while another might find the sweetness pleasant. “Too much oak in this wine,” you might say, but the person sitting next to you finds the rich, oaky flavors add complexity and body to an otherwise ordinary wine. In reality, of course, this "flaw" is just a matter of opinion.

True flaws, known as objective flaws, occur because of chemical imbalances in the finished products. Wine is primarily of water (80%–90%). The remaining 10%–20% is made up of hundreds or even thousands of different chemical or molecular components. Here, problems may arise.

The first type of subjective flaw is off-odors resulting from sulfur compounds. Sulfur has been used since Roman times as a preservative. However, in the wrong concentration, bad things happen. Sulfur dioxide (SO2)* is characterized by a pungent smell of burnt matches, often accompanied by an unpleasant tickling sensation in the nose and throat. The effects of SO2 are directly related to pH. The more acidic the wine, the more pronounced the sulfur dioxide will be. Another compound, hydrogen sulfide (H2S), is characterized by an odor of rotten eggs, resulting from the reduction of elemental sulfur. Yeasts need nitrogen to grow and multiply. In a nitrogen-deficient must, yeasts scavenge for this element by breaking apart amino acids containing nitrogen. In the process, sulfur is released as H2S. A third variant is mercaptan, which is often described as a garlic- or onionlike aroma, and is formed when SO2 and ethyl alcohol molecules combine.

Next, let’s examine some of the flaws related to wild yeasts. Yeast is an integral part of the winemaking process. Most winemakers prefer to inoculate with cultivated yeast instead of using native (wild) yeasts in order to maintain a consistent product. Occasionally, wild strains like Brettanomyces (brett) or Dekkera will infect a winery. In small amounts, brett can actually be a pleasant experience contributing aromas such as bacon fat, barnyard, tar, leather and clove. In some of the terroir–driven wines of France (like Burgundy and Rhône) brett might have been responsible for some of the traditional descriptors associated with these wines. In large amounts brett is likely to produce aromas of Band-Aids, dirty socks, creosote and burnt beans. Yuck! Dekkera in high concentrations will produce aromas of cement or dirt, not something one would want in a wine. Usually this fault occurs because of unsanitary conditions in the winery.

Another defect that will generate a bad experience with wine is volatile acidity (VA). Acidity is a natural component of wine. Volatile acidity differs from fixed acidity in that the acid component in fixed acidity is sensed on the palate. Tartaric and malic acid are examples of fixed acidity. Volatile acids, on the other hand, make their way into the air and can be detected by the nose. A concentration of acetic acid will result in odors of vinegar, and ethyl acetate (acetone) smells like nail polish. One of the ways (VA) gets into wine is through the fermentation process. Microbes such as lactic acid bacteria and wild yeasts are exacerbated by too much oxygen.

Our next imperfection results from the improper handling of wine. Although wine is a sturdy fluid, there are a few things that can be very detrimental to the finished product. Oxygen and heat are two big enemies of fine wine. When a wine has been exposed to air for a long time, it becomes oxidized. This process, results in the wine turning colors, usually dark amber or brown, and exhibiting a nutty, spoiled aroma. There will be almost no fruit left. When a wine is left in the heat too long, it is said to be maderized, or cooked.

One of the most common flaws is known as cork taint. It is said that anywhere from 3% to 10% of all wine is affected. This is caused during the sanitizing of a natural cork. Due to the porous nature of cork, sometimes microbes are trapped in those pores. When the corks are bleached, a reaction with microbial mold forms a compound known as trichloroanisole 2,4,6 (TCA). Odors of wet cardboard, damp musty basement and mold will be prevalent. TCA is perceptible in the parts-per-trillion range. Winemakers have found ways to combat cork taint by using alternative enclosures such as synthetic corks and screw caps.

Because of wine’s complex nature, there are many other things that can go wrong. The thing to remember is if you try a bottle that is flawed, that does not necessarily mean that all the wines from that producer will be flawed. The best thing to do is to return the bottle and try another. Chances are, you will not be disappointed.

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