Today’s wine consumer encounters far less wine faults than those of years past thanks to improvements to sanitation in wine cellars and technological advancements in winemaking. Today, consumers are far less likely to encounter “off” wines because winemakers take great care to ensure that their products are “clean”.
Tolerance for certain scents, flavours and textures varies for a number of reasons, but judging whether or not a wine is to your taste is not the same as making a quality judgement towards that wine. The first step in wine tasting is evaluating a wine’s cleanliness; it’s as simple as looking and smelling. If the wine is faulted, you’ll be able to stop there and save your taste buds, so you can enjoy a good bottle.
Here are some of common wine faults that winemakers and wine consumers have to deal with:
Cork Taint (mouldy, damp smell)
The fault that most readily comes to the nose is cork taint, or 2,4,6-Trichloroanisole (TCA). It is by far the most noticed wine fault or at least the one that gets most of the press. It is so well known that when a wine is “off”, many consumers will simply say that it is corked, when it could be affected by a number of different faults. TCA is a chemical compound that makes it’s way into the bottle somewhere along the production line; the most common route is through the cork closure itself, although the compound may also be present in the winery so a wine under screw cap could still be affected by TCA.
You can’t tell if a wine has cork taint simply by looking at it; it’s only perceivable to the nose. It smells like dampness: like an old mouldy basement or a stinky wet dog. Unpleasant to say the least and in varying levels of intensity. Once you’ve smelled a “corked” wine, you’ll be able to pick them out in the future; my tip is to trust your initial sniff; if you think the wine may be corked, it usually is. Perhaps let the wine sit a moment and come back to it; TCA wont dissipate and I usually find it becomes more obvious as the wine sits. If you are doubting yourself, ask a Somm to confirm.
From a consumer’s point of view, there isn’t much to be done to avoid cork taint. When you come across it, return the wine to the store or have the bottle replaced at a restaurant. Any restaurant with a well established wine program in place will replace the bottle and would never pour a stinky wine by the glass.
Sulfur compounds (burnt, rotten eggs, cabbage smells)
Sulfur dioxide (SO2) is naturally occurring in grapes and it us used in both the vineyard and during winemaking to protect the wine from oxidation (another common fault that occurs when wine is exposed to too much oxygen). Too much SO2 in a wine smells like a just struck match and though it is initially unpleasant, it can burn off once the wine is exposed to air.
The other sulphur compound, dihydrogen sulfide (H2S), is a major problem in winemaking and can be traced back to the vineyard. It is a by-product of lack of nitrogen in the vineyard and residual sulfur dioxide on grapes that carries over into fermentation when the winemaking yeasts become “stressed out” during fermentation and release hydrogen sulphide. If the winemaker feeds the yeasts appropriate nutrients they will essentially chill out and stop forming H2S. Copper sulfate has proven to remove H2S and in the past, when copper pipes and fittings were used in winemaking, it would have helped with this problem. If H2S is left untreated the wine basically turns into a stink bomb because of the formation of mercaptans (even stinkier than H2S), and therefore becomes unsmellable and unsellable.
Volatile Acidity (vinegar smell and taste)
A lot can go wrong in the winemaking process that could potentially harm the wine. According to Grand Pre Winery’s winemaker Jurg Stutz, volatile acidity in the finished product is a major winemaking concern. He says that it is unlikely that there will be any problems with VA if the crop is generally healthy and any disease-affected grapes are removed plus the work environment and processing equipment are clean while sulphur levels are kept at an appropriate range and tanks and barrels are full. Note that some winemakers encourage slightly higher levels of acetic acid in their wine for the complex quality it offers, making the wine more aromatic. This is a stylistic choice and carefully controlled; otherwise, that wine becomes an expensive bottle of vinegar!
Protein Instability (hazy, cloudy)
Another concern for winemakers is the presence of unstable proteins in the finished wine. This could happen if proteins from the grapes are carried over into the wine, causing a haze to develop if the bottled wine is subjected to temperature extremes. The protein molecules are too small to be visible to the naked eye but under certain conditions they polymerize (link together) and become larger particles that are too large to stay suspended in the wines, forming a haze. Winemakers refer to this protein haze as “hot instability” because it is caused by warm temperatures. This is an issue for both white wine and rose so winemakers fine the wine with Bentonite to stabilize it before bottling. Protein instability is rarely an issue in for red wines as they contain “phenolic compounds” (like tannins) that react with grape proteins during fermentation and eventually precipitate out of the wine.
Refermentation (bubbles)
Unless you’ve purchased a Champagne, Cava or the the like, you might not be thrilled to open your bottle of Chianti Classico to find out that it is bubbling away. Refermentation is a concern for winemakers, especially if there is any residual sugar in the finished wine. Sugar + yeast = bubbles in a bottle, so care must be taken to remove all yeast before bottling- this is where filtering comes in.
Wine Folly has even more to say on this subject. Check it out here.