If we loved wine only for its fruit, we would just drink juice. And if that were the case, there would be magazines, books, movies, collectors' guides and appreciations on the subject of juice. No, we love wine, partly for the alcohol, but also partly for the wild diversity of flavors. Many of them are bizarre and special.
The first flavors we learn about in wine are fruit aromas, perhaps because they are the most satisfying. But when you smell a wine, it's hard not to notice all the special, weird flavors, including:
Leather, plasters, cloves, boiled cabbage and diapers.
If you are scientific and curious, you can learn to identify many flavor compounds (including "effect compounds") in wine. Next time you have a glass of wine in front of you, see if you can spot any of these bizarre flavors:
Volatile acids
Compounds: acetic acid and ethyl acetate
How it smells: pungent, vinegar, fruity raspberry or cherry, nail polish remover
How it tastes: sharp or spicy mouthfeel, often toward the end of the drink
As the name suggests, volatile acidity indicates volatility in wine, a signal that things are going badly. Acetic acid builds up in wine when too much oxygen is exposed during winemaking and is usually caused by vinegar-making bacteria. Volatile acidity is considered a malfunction at higher levels (1.4 g/L in red wine and 1.2 g/L in white wine) and can smell acrid like nail polish remover. But at lower levels, it can add fruity-smelling raspberry, passion fruit or cherry-like flavors. Wines that have long fermentations (1 month or more), such as Amarone della Valpolicella, Ice Wine and Barolo generally accumulate higher levels of volatile acidity.
TIP: Some people are more sensitive to volatile acidity than others and dislike wines with even the smallest amounts present.
Reduction (sulfur compounds)
Compounds: dimethyl disulfide, dimethyl sulfide, hydrogen sulfide and ethane thiol
How it smells: truffle, mushrooms, radishes, green olives, rotten eggs, onion, cooked cabbage, canned corn or burnt rubber
How it tastes: a very subtle creaminess to the texture of the wine
There is some fear of sulfur and its role in wine due to certain people's sensitivity to sulfites. However, reduction (sulfur compounds) occurs naturally in wine as a result of fermentation (even without sulfite additives) and contributes to a wine's aromas. The cause of reduction is lack of oxygen during fermentation where a sulfur atom is used to complete chemical processes instead of an oxygen atom. At low levels, reduction causes the following aromas: truffle, mushroom, radish and green olive-like odors. These are accepted as positive attributes and increase complexity in the wine. At higher levels, reduction is seen as a flaw, giving wines a sharp smell of rotten eggs, onion, garlic, boiled cabbage, canned corn, or even burnt rubber.
TIP: If these smells don't disappear within 30 minutes of opening and pouring the wine, you have a wine bug on your hands! Sometimes something made of silver in your glass can help reduce the odor ...
Brettanomyces
Compounds: 4-Ethylphenol (4-EP) and 4-Ethyl Guaiacol (4-EG)
How it smells: cloves, cardamom, medicines, band-aids, leather saddles
Brettanomyces is a wild yeast that produces particularly distinct aromas that range from subtle clove and spice aromas to pungent scents of horse stable, medicinal plasters and saddles. The latter aromas are why Brettanomyces is widely considered a wine fault - although some people who like the woody, leathery aromas produced at lower levels. Brett was once much more common before we had the technology to properly clean winemaking equipment. Therefore, some old world wines have historically been known to have Brett-like flavors. However, if you taste a wine with these aromas, it is definitely caused by wild yeasts like Brett.
Acetaldehyde
How it smells: candied green apple, apple sauce, bruised apple, Brazilian nut, wet paint
How it tastes: tawny and somewhat sharp on the mid palate and finish
Admittedly, it seems a bit strange to mention some kind of poison as an aromatic component in wine. Maybe that's why it's good to drink modestly. That said, acetaldehyde is present in very small amounts in most wines (dry wines usually have between 30 and 80 parts per million) and in Sherry and other oxidized wines it is slightly more (300 parts per million).
Acetaldehyde delivers pleasant fruity notes reminiscent of cooked apples at lower levels, and at higher levels it smells more like bruised or rotten apples, Brazilian nuts, almonds and even wet paint.
Afterword
Now that we have established that wine is not just fruits and flowers, we can review its aromas with a new setting of expectations. Have fun smelling!
