Wine Faults - When Wine Doesn't Taste as It Should

Short Definition

Wine faults are undesirable sensory deviations caused by errors in production or storage, or by microbiological contamination. They negatively affect the aroma, taste, and texture of wine and can in extreme cases make it undrinkable.

At a glance:

• Category: Wine quality, sensory evaluation, production
• Origin: Production or storage errors
• Synonyms: Off-notes, wine defects, wine flaws
• English: Wine faults, wine defects

Detailed Explanation

Wine faults must be distinguished from wine style — a fault is an objective impairment of quality, not a matter of taste preference. While some people prefer dry wines and others sweet, a corked wine is objectively defective.

Categories of Wine Faults:

1. Microbiological faults Caused by unwanted microorganisms (bacteria, yeasts, moulds)

2. Chemical faults Caused by unwanted chemical reactions or compounds

3. Physical faults Caused by light, heat, oxygen, or improper storage

4. Production faults Caused by errors in winemaking or hygiene deficiencies

The Most Common Wine Faults

1. Cork Taint (TCA Contamination)

Cause: 2,4,6-trichloroanisole (TCA), usually from contaminated natural corks

Recognition:

• Smell: Wet cardboard, musty cellar, mouldy cork
• Taste: Flat, devoid of fruit, cardboard-like aftertaste
• Texture: Watery, depleted

Frequency: 2–5% of all bottles with natural corks Claimable: Yes, always

Intensity: Varies from slight (only suppressing the fruit) to extreme (completely undrinkable)

2. Oxidation

Cause: Excessive, uncontrolled exposure to oxygen

Recognition:

• White wine: Dark, amber colour; Sherry-like notes; flat taste; loss of freshness
• Red wine: Brownish, brick-red colour; vinegar, rotting fruit; flat, without structure

Causes: Defective cork, overly warm or fluctuating storage, wine that is too old, production errors

Claimable: Yes for young wines; in very old wines, slight oxidation can be stylistic

3. Reduction (Sulphur Off-Notes, "Brett-like" Reduction)

Cause: Hydrogen sulphide (H2S) and mercaptans from anaerobic conditions

Recognition:

• Smell: Rotten eggs, struck match, burnt rubber, garlic, cabbage
• Taste: Sulphurous, unpleasant

Intensity: From slight (disperses on decanting) to severe (persistent)

Claimable: Moderate to severe yes; slight cases may be resolved by decanting

4. Volatile Acidity (Vinegar Taint)

Cause: Acetic acid bacteria (Acetobacter) convert alcohol into acetic acid

Recognition:

• Smell: Vinegar, nail polish remover, pungent
• Taste: Sour, sharp as vinegar, burning

Causes: Poor hygiene, defective barrels, excessive oxygen contact

Claimable: Yes, always

5. Brettanomyces ("Brett")

Cause: The yeast Brettanomyces, which produces 4-ethylphenol and 4-ethylguaiacol

Recognition:

• Smell: Horse stable, sweat, leather, medicinal, sticking plaster
• Taste: Animal, metallic

Controversy: In small amounts, considered by some as a "terroir character" (e.g. certain Châteauneuf-du-Pape), but regarded as a fault at higher concentrations

Claimable: Yes, when pronounced

6. Refermentation (Bottle Fermentation)

Cause: Unintended fermentation of residual sugar in the bottle

Recognition:

• Slight carbonation (fizzing on the tongue in a still wine)
• Possibly cloudy wine
• Slightly yeasty

Claimable: Yes for still wines (except Vinho Verde, where slight carbonation is typical)

7. Heat Damage (Cooked Wine)

Cause: Storage at excessively high temperatures (above 25°C)

Recognition:

• Smell: Cooked fruit, jam, caramelised
• Taste: Flat, alcoholic, lacking freshness
• Appearance: Cork often protruding or leaking

Causes: Transport or storage in heat

Claimable: Yes

8. Light Strike ("Goût de Lumière")

Cause: UV light exposure, especially in white wine in clear bottles

Recognition:

• Smell: Wet fur, skunk, burnt hair, sulphur
• Taste: Unpleasantly sulphurous

Causes: Storage in a bright room, display in a shop window

Claimable: Yes

Practical Significance

At Tasting

Wine faults often show up very clearly in the finish — while the first impression may still be acceptable, faulty wines almost always leave an unpleasant aftertaste.

When Buying

With expensive wine: always check that the wine is fault-free. In a restaurant you have the right to return a faulty wine — the sommelier should accept this without discussion.

When Storing

Many wine faults arise from improper storage:

• Too warm: Oxidation, heat damage
• Too bright: Light strike
• Standing upright: Cork dries out, causing oxidation
• Fluctuating temperature: Accelerates aging, promotes faults

Examples & Application

How to Tell Whether a Wine Is Faulty

Checklist for wine assessment:

Visual:

• Is the colour unusual for the type and age? (e.g. brownish young white wine)
• Is the wine cloudy or does it have particles in suspension? (except in natural wines, where this is normal)
• Is the cork protruding abnormally? (a sign of heat damage)

Olfactory (smell):

• Does the wine smell of vinegar, rotten eggs, cardboard, horse stable?
• Are the fruit aromas muted or absent entirely?
• Is the smell pungent or unpleasant?

Gustatory (taste):

• Does the wine taste flat, without fruit?
• Is it excessively sour or vinegary?
• Does it leave an unpleasant, chemical aftertaste?

If in doubt: Compare with a second bottle of the same wine. Wine faults normally affect only individual bottles (except in cases of production errors).

Practical Tips

1. In a restaurant: If you suspect a faulty wine, ask the sommelier for their assessment. Professionals recognise faults immediately and should exchange the wine without fuss.

2. At home: Keep the faulty wine and cork and contact the retailer. Reputable retailers will refund or exchange.

3. For cork taint: Many producers have a goodwill policy. Often a photo of the label plus a description of the fault is sufficient.

4. Decanting test: Some minor faults (reduction, sulphur notes) dissipate on decanting. If the wine improves after 30 minutes of aeration, it was only a minor defect.

5. Training: Some wine schools offer "fault workshops" where faulty wines are tasted specifically to train recognition.

Historical Context

Wine faults are as old as winemaking itself. In pre-industrial times, many wines were far more fault-ridden than today — vinegar taint and oxidation were widespread. The development of sulphur as a preservative in the 18th century was a breakthrough.

Cork taint was only identified as a systematic problem in the 1980s when TCA was identified as its cause. This led to massive efforts by the cork industry to reduce the problem and to the development of alternatives such as screw caps and synthetic corks.

Modern oenology has drastically reduced the frequency of wine faults. Better hygiene, temperature-controlled fermentation, SO₂ management, and quality controls make wine faults rarer. Nevertheless: 3–5% of all wines have noticeable defects.

The trend towards natural wines has reignited the debate: what is a fault, and what is a style? Some "Brett" notes or slight oxidation are appreciated as character by natural wine enthusiasts, but regarded as faults by classical wine drinkers.

Country- and Region-Specific Characteristics

France: High quality standards, but also tolerance for some "faults" as stylistic elements (e.g. Brett in certain appellations). The term "défaut" carries a clearly negative connotation.

Italy: Strong regional differences. Northern Italy (Piedmont, Tuscany) has very high standards, while greater tolerance prevails in some southern regions.

Germany: Extremely high quality controls through official wine testing. Faulty wines do not receive an approval number and cannot be sold as quality wine.

USA: Very low tolerance for wine faults. The right of return is widespread. Critics such as Robert Parker rate faulty wines very low.

Australia/New Zealand: Pioneers of screw caps (over 90% of New Zealand wines), which has virtually eliminated cork TCA.

Related Terms & Links

• Tasting: Systematic tasting helps reliably identify wine faults.

• Aroma: Wine faults manifest primarily as off-aromas that overlay or distort normal wine aromas.

• Finish: Faulty wines often show particularly unpleasant notes in the finish.

• Oxidation: One of the most common wine faults, especially with improper storage.

• TCA: 2,4,6-trichloroanisole, the main cause of cork taint.

Frequently Asked Questions & Misconceptions

Question: Is every wine I don't like faulty?

Answer: No! There is a significant difference between "I don't like it" (style, personal preference) and "it is faulty" (objective defect). An ultra-dry Riesling with high acidity may not suit your taste but is not faulty. A wine that smells of vinegar or wet cardboard, however, is objectively defective.

Question: Is sediment (deposit) a wine fault?

Answer: No, sediment is not a fault but a natural product of maturation in high-quality red wines. It consists of precipitated tannins and colour compounds. This is why aged wine is decanted. Only in young wines or with heavy cloudiness might it indicate a problem.

Question: Can you "rescue" a faulty wine?

Answer: It depends on the fault. Slight reduction (sulphur notes) may disappear with decanting. Copper coins placed in the wine can bind sulphur compounds (an old winemaker's trick). However: cork taint, vinegar taint, or heavy oxidation are irreversible. The wine remains faulty.

Question: Why do some producers refuse to exchange bottles with cork taint?

Answer: Unacceptable! With demonstrable cork taint, a complaint is justified. Reputable producers and retailers always exchange or refund. The fault lies with the cork manufacturer, not the winemaker, but the producer bears responsibility for their product.

Question: Are wines with screw caps free from faults?

Answer: They are free from cork TCA, but not from all other faults. Oxidation, reduction, Brett, vinegar taint, etc. can all occur with screw caps. However, the fault rate is significantly lower than with natural cork (approx. 1% vs. 3–5%).

Expert Tip

Trust your nose! The nose is our most sensitive sensory organ and often recognises wine faults more reliably than the taste sense. If a wine smells "off" at first sniff — not just different, but genuinely unpleasant — it is probably faulty.

My most important practical tip: develop your "fault profile." Visit a wine fault workshop if possible (many wine schools and chambers of commerce offer them). Faults are deliberately introduced into wine so that you learn what cork TCA, vinegar taint, Brett, etc. smell and taste like. After such a workshop, you will recognise faults immediately.

For restaurant visits: don't be afraid to return a wine! You are paying for a flawless product. A good sommelier will take your concern seriously, smell it themselves, and exchange it without discussion. If they argue, that is a sign of poor professionalism. For obvious faults (TCA, vinegar), there is no room for debate.