What Are Wine Faults — And Why Should We Care?
Even the most exquisite terroir and masterful vinification can be betrayed by something as minor as a faulty cork or a rogue microbe. Wine faults are a part of wine tasting that many dislike discussing—yet they’re essential to identify if we aim to enhance our understanding and appreciation of wine.
This is not simply about detecting flaws that ruin a wine, but recognising when a characteristic steps out of balance, revealing the line between complexity and defect. Whether you’re a casual enthusiast or an aspiring sommelier, knowing how to distinguish a fault from a natural variation is a core competency in serious tasting.
What Defines a Wine Fault?
A wine fault is a specific undesirable characteristic that results from issues in winemaking, storage, or bottling. Unlike mere stylistic differences or personal preferences (say, the presence of high VA in a natural wine), a fault is generally viewed as objectively detrimental to the wine’s quality.
Importantly, faults differ from wine flaws. A flaw may be seen as a minor irregularity or idiosyncrasy (slight oxidation in an old Riesling, for example), whereas a fault typically interferes with both aroma and taste in ways that obscure the wine’s intended expression.
Common Wine Faults and How to Recognise Them
Let’s break down the most frequently encountered faults and how to detect them during tasting.
Cork Taint (TCA – 2,4,6-Trichloroanisole)
What it smells like: Wet cardboard, damp basement, or mouldy newspaper. It mutes the fruit intensity significantly.
How it happens: TCA is usually formed when natural cork interacts with chlorinated cleaning products in a winery. Ironically, the cork intended to preserve the wine ends up spoiling it.
Detection Tip: If you detect little to no fruit, and that curious wet cardboard note wafts up, don’t second-guess yourself. This is one of the most common and immediately recognisable faults.
Oxidation
What it smells like: Bruised apples, sherry, or nuts in wines that aren’t fortified or meant to be oxidative.
How it happens: Excessive exposure to oxygen during winemaking or due to faulty closures can lead to premature oxidation. Some oxidation is deliberate (e.g., Jura Vin Jaune), but when unintentional, it suggests mismanagement in bottling or ageing.
Detection Tip: Start with the colour—whites turn amber, reds lose vibrancy. On the nose, if you smell flat apple or stale nut aromas in a young wine, it’s time to raise red flags.
Volatile Acidity (VA)
What it smells like: Vinegar, nail polish remover, or ethyl acetate.
How it happens: VA stems from acetic acid and related esters formed by the metabolism of spoilage yeasts and bacteria—especially in wines with poor hygiene during fermentation.
Detection Tip: A faint vinegar note in small quantities can add complexity, particularly in natural wines or Sauternes. But if the smell dominates or burns the nose? It’s no longer a nuance—it’s a fault.
Reduction
What it smells like: Struck match, rotten eggs, burnt rubber, boiled cabbage.
How it happens: Reduction occurs when wines are deprived of oxygen, particularly in reductive winemaking environments like sealed stainless-steel vats or screwcap closures. Sulfurous compounds build and become aromatic nuisances.
Detection Tip: Unlike many faults, some reduction can be temporary. Swirling the glass vigorously may release the foul aromas. If they persist, though, you’ve got reductive spoilage.
Brettanomyces (« Brett »)
What it smells like: Barnyard, sweaty saddle, plaster, Band-Aids. Some say « funky », others say « infected ».
How it happens: Brettanomyces is a yeast that can contaminate barrels or tanks. While it’s tolerated—even embraced—in certain styles (hello, rustic Rhône!), excessive Brett masks freshness and varietal character.
Detection Tip: Again, this is a question of threshold. Some herbal reds (particularly Syrah and Mourvèdre) wear a bit of Brett well. But when it wipes out any trace of fruit, it’s a sign the culture has overwhelmed the wine.
Mousiness
What it smells like: Actually, nothing—at first. Mousiness is a retro-nasal fault; you taste it after swallowing, manifesting as a cereal-like, hamster-cage aroma.
How it happens: Usually seen in low-sulfur natural wines, the fault is linked to spoilage bacteria creating nitrogen-containing compounds on the palate.
Detection Tip: If after tasting, you notice an off-putting yeasty or savoury aftertaste lingering unpleasantly on the palate, that’s likely mousiness. Some people are anosmic to it—but once you know the flavour, you won’t un-know it.
Refermentation in Bottle
What it smells like: Yeasty, unfresh, or slightly sharp on the nose. You may hear or see fizz where none should be.
How it happens: If residual sugar and active yeast are bottled together (often in semi-sweet wines), they may ferment in the bottle, leading to bubbles and cloudy sediment.
Detection Tip: Listen to the wine. Pop and fizz in what should have been a still wine? Time to reevaluate the wine’s storage or stabilisation protocols.
Is It Style or Fault? A Necessary Distinction
One of the recurring dilemmas when assessing wine faults is parsing the difference between a stylistic signature and a genuine defect. For example, oxidative notes are prized in traditional Rioja, and Brett is virtually endemic in some classic producers of Châteauneuf-du-Pape. Does that make it wrong? Not necessarily—it’s contextual.
One rule of thumb I use is to ask: does this element enhance complexity and reflect place and process, or does it obscure fruit and imbalance the structure? Faults erase wine’s identity. Great wines may have quirks, but those quirks elevate rather than overwhelm the ensemble.
Can Faulted Wines Be Salvaged?
In some cases, yes—but only partially. Decanting may help reduce reductive aromas; chilling might mute volatile acidity a bit. But fundamentally, wine faults stem from chemical realities. No amount of swirling, airing or prayer can fix TCA once it’s present.
The best prevention lies in careful sourcing. Producers who value hygiene, proper storage, and modern bottling techniques are less likely to ship flawed bottles. If you’re investing in cellar-worthy wines, don’t be shy about asking questions. When I worked as a sommelier, I always noted which domaines had a reputation for clean bottling and which… didn’t.
Final Tasting Advice: Trust Your Senses, But Train Them
Being able to detect wine faults isn’t about appearing clever at a dinner party. It’s about developing sensory awareness and deepening our connection to the wine in the glass. Don’t dismiss a wine too quickly—sometimes what seems off may just be unusual. But also don’t override your instincts because the label or producer is prestigious.
Train with flawed samples if possible. Some producers and wine schools offer dedicated fault kits containing micro-doses of TCA, VA, Brett and others to help calibrate your palate. It’s not the most glamorous part of tasting, but it’s essential to developing discernment.
After all, appreciating great wine begins by knowing what can go wrong—and why, when it all goes right, that first sip can be pure magic.