Ah! Pulling the cork from a bottle and anticipating that glass of wine... and then as you pour the wine into a glass, you are greeted by a foul smell. What has gone wrong with the wine? Wines can develop foul odors and tastes for a variety of reasons, and an understanding of these aromas would require knowledge of organic chemistry. Instead, below are simple explanations for any wine drinker who has ever encountered a wine that smelled like nothing one would want to drink.
Oxidation causes a loss of freshness and fruit, browning of the wine along with flat tired taste and acetaldehyde aroma (acetaldehyde smells like Sherry). It may also cause a caramel or beef extract character.
Subjecting a wine to heat causes a nasty baked fragrance and flavor. The wine will turn brown and the fruity character will be greatly reduced. Heat causes the degradation of carbohydrates and caramelization of sugars. It can also make the wine smell of cooked cauliflower and asparagus. Don't leave wine in the trunk of your car and don't store it in a heated area.
Sulfur Dioxide and Reduction
Sulfur dioxide is absolutely necessary in winemaking but sometimes it may cause faults. Too much sulfur dioxide may result in a sharp, pungent smell, acrid pricking in nose and mouth, especially the back of the throat. Hydrogen sulfide (as a result of excessive sulfur added late to grapevines to prevent mildew) smells like rotten eggs or dirty drains, while Mercaptans (as a result of sulfur dioxide combining to create larger compounds) have a strong, unpleasant smell of garlic, onions and rubber, and sometimes a skunky smell.
Acidity is important in a wine and contributes to freshness, balance, body and bottle ageing. There are fixed and volatile acidities; the volatile acidity is necessary and adds complexity but is a fault in excess causing an ethyl acetate (nail varnish) smell and a vinegar taste.
Cork taint is a musty, dank fungal smell in wine that may also be described as wet cardboard. At low levels it may not be perceptible as cork taint, but may rob the wine of fruit character. Recognition and detection thresholds vary with the type of wine and the sensitivity of the taster. Cork taint is caused by 2,4,6 trichloranisole (TCA) that has an affinity for cork, which is highly absorbent. However, it may also be found in wood and barrels used in the cellar. TCA has a musty odor at only a few parts per trillion.
Bacterial and Yeast Contamination
Sometimes a wine may have a bacterial growth as evidenced by off-smell, oily look and taste, dull color and bitterness. One of the most common problems is Brettanomyces, or Brett. This wild yeast is found in almost all vineyards and wineries. In small amounts it can add complexity but at high levels is causes haze, unpleasant aromas and flavors of barnyard, Band-Aid®, spicy, sweaty saddles and wet wood. On the palate there is a medicinal taste, oily mouth feel and off flavors as aromas.
Vegetal Aromas and Flavors
Often a wine will smell and taste of green bell peppers, green stalks or green olives. These compounds come from unripe fruit. Pyrazines are responsible for the green bell pepper characteristic and are found in wines such as sauvignon blanc and cabernet franc. However, they are a fault a high levels.
Keep in mind that the number of wines with off-putting aromas is a small fraction of the total number of wines produced each year. Also, individuals vary greatly in their sensitivities to different aromas, and certain off aromas can actually be attractive when present in tiny amounts.
Thank you, all, for taking your time to read my contributions about wine on Marilee's site. I have a great time selling wine for Costco, showing new wines to old customers, meeting new customers and introducing new wine fledglings to wines I think he/she would like. I hope 2011 will be a wonderful year for you -- full of joy, love, and good wine!!
Certified Wine Professional
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