Oh, if only any of these vials smelled as good as bacon.
You may have seen my post about Le Nez du Vin, the wine-smelling practice kit. Well, I liked the master aroma kit so much that I recently purchased the faults (les défauts) kit. And boy, does it stink – onions, rotten apples, moldy earth, oh my. It’s great to be able to recognize the delicious aromas in wine, but it’s also important to recognize faults – no sense in wasting your time on a bad bottle, right?
The faults in the kit are broken into different categories and today I’m going to share with you the ones that are related to harvest and those that come about through exposure to oxygen.
1. Vegetal (trans-2-hexanal). Underripe grapes, insufficient destalking (leaving too many stems in the mix) or overpressing (too much contact with stems and other undesirable parts)at harvest can all be culprits, giving wine sharp notes of green beans or green pepper. This scent highlights the subjective nature of tasting – for example, I often enjoy a little bell pepper aroma in my Cabernet Francs. If the wine contains more than 0.5 grams/liter of trans-2-hexanal, however, the balance of aromas will be out of wack and the taste of leaves and stalks will be overwhelming.
2. Rotten apple (acetaldehyde). The smell of rotten apples, walnuts or musty yeast can come about from large amounts of acetaldehyde, which will form if the wine is exposed to oxygen. Not only does it smell gross, acetaldehyde can also cause headaches. If a wine is left in contact with the air, a film of micro-organisms (candida mycoderma) will form. They’re a contaminating yeast that’s always lurking in wineries – on the walls, the ground, the sides of the vats – and they’ll cause the alcohol in the wine to oxidize. This is bad because there’s less alcohol (duh) and the acidity will increase, therefore adulterating the wine, leading to a formation of acetaldehyde.
3. Vinegar (acetic acid). When a wine tastes bitter, sour or vinegary, it could be from a contamination of acetic acid, caused by acetic bacteria, now commonly referred to as acetobacter. While good for making vinegar, these little buggers are not good for wine – they make it acrid and reduce its alcohol level. They require oxygen to turn the alcohol in the wine into acetic acid, so winemakers will always make sure to top off their barrels (so there’s no head space containing oxygen) and that there’s no leaks in any of their barrels. The formation of acetic acid will also depend on the temperature, the wine’s pH and whether or not it’s been treated with sulphur.
4. Glue (ethyl acetate). Acetic acid can react with the alcohol in the wine to form an ester: ethyl acetate, which will give the wine an “eau de Elmer’s”. This reaction will also reduce the alcohol levels in the wine as well as increase its volatile acidity (often called VA; organic acids in wine – often acetic – at high levels will give vinegary sensation – see #3). Once acetic acid is doing its work, it can’t be stopped – prevention is the cure: clean winemaking equipment, avoiding air contact, using sulphur dioxide to eliminate acetic bacteria and so on.
5. Soap (decanoic acid). Fatty acids produced by yeast during the vinification process can turn up in the wine as salts, often referred to as “soaps”. You can often find a candle or other waxy aroma in young white wines and young spirits. Semi-related; some use the term soapy when the wine is dull or has a disagreeable flavor – often from low acidity.
Tune in soon for faults caused by sulphur, phenols and fungi.