18.2 Common Wine Faults
Key Takeaways
- Cork taint (TCA) smells of damp cardboard or mouldy cellar and mutes fruit; it comes from contaminated cork (or rarely other materials), not from “the wine going off” in bottle heat alone
- Oxidation browns colour, flattens fruit, and adds nutty/sherry-like or vinegar-adjacent tiredness when unwanted; causes include poor closure, low fill, age, or excessive oxygen exposure
- Reduction shows struck match, onion, rubber, or rotten-egg notes from sulfur compounds; mild reduction may blow off with swirling or decanting, while severe reduction remains faulty
- Volatile acidity (acetic acid/ethyl acetate) suggests vinegar or nail varnish; Brettanomyces adds animal, bandage, or spicy farmyard notes that can overwhelm fruit at high levels
- Out-of-condition wine tastes tired or prematurely aged; high SO₂ gives a pungent struck-match/choking sensation—recognise faults so you can advise exchange, alternative bottles, or storage lessons
Fault recognition sits at the heart of professional service advice. Customers often describe a fault as “the wine is corked” when they mean any unpleasant bottle. Your job is to name the fault accurately, explain the likely cause in plain language, and decide whether the bottle should be rejected, aired, or accepted as a stylistic quirk at low intensity.
On tasting exams and in theory stems, distinguish fault (negatively affects enjoyment and is not intended) from character (e.g. deliberate oxidative Sherry, modest struck-match reduction in some premium whites, light spice from oak). Intensity and context decide the call.
Cork taint (TCA)
2,4,6-trichloroanisole (TCA) and related compounds cause classic cork taint. Recognition cues:
- Aromas of damp cardboard, wet newspaper, mouldy cellar, or musty cupboard
- Fruit aroma muted or wiped out; palate short and dull
- Often noticed immediately on nosing the glass or cork
Causes: contamination associated primarily with natural cork (chlorine-related compounds interacting with moulds), though TCA can also appear from contaminated winery wood, barrels, or packaging in rare cases. Screw-cap wines are not immune to all musty faults, but classic cork taint is strongly linked to cork closures.
Advice: replace the bottle. Airing does not remove TCA. Do not blame the customer’s glassware first if the damp-cardboard signature is clear.
Oxidation
Unwanted oxidation occurs when wine has had too much oxygen relative to its protective SO₂ and phenolic/buffer capacity.
Recognition:
- Whites: deepening gold to brown; loss of fresh fruit; nutty, apple-cider, or tired sherry-like notes when not intended
- Reds: brick/brown rim beyond age expectation; dried-out fruit; flat, sometimes sharp or stale finish
- Palate lacks freshness; acidity may seem disjointed
Causes: faulty or dried-out closure; upright long-term storage of cork-sealed bottles; high storage temperature; low fill level; excessive racking/ageing without protection; bottle left open too long. Deliberate oxidative styles (Oloroso Sherry, some vin jaune, certain amber wines) are not faults—check context.
Reduction
Reduction refers to sulfur-related compounds formed in low-oxygen conditions (certain yeast metabolism, lees ageing, reductive winemaking, some screw-cap environments).
Recognition (from mild to severe):
- Struck match, smoke, flint (can be acceptable in small amounts in some styles)
- Onion, garlic, boiled cabbage
- Rubber, burnt rubber
- Rotten eggs (hydrogen sulfide)—clearly faulty
Causes: nutrient-stressed ferments, heavy lees contact without enough oxygen management, very tight closures limiting oxygen ingress. Mild reduction may dissipate with swirling, time in glass, or decanting. Severe reduction persists and should be treated as a fault—offer another bottle rather than insisting the guest “just wait.”
Volatile acidity (VA)
Volatile acidity is mainly acetic acid (vinegar) and ethyl acetate (nail varnish / solvent).
Recognition: vinegar, balsamic sharpness beyond freshness; nail-polish remover; at high levels the wine smells solvent-like and tastes sharp and hollow.
Causes: acetic acid bacteria activity with oxygen exposure (damaged fruit, poor hygiene, partially filled vessels, leaky barrels). Small amounts can add lift in some sweet wines; obvious vinegar/nail-varnish character is a fault.
Brettanomyces (“Brett”)
Brettanomyces is a spoilage yeast that produces volatile phenols.
Recognition:
- Bandage, antiseptic, medicinal
- Sweaty saddle, barnyard, animal
- Clove/spicy notes that can tip from complexity into dirtiness
- Fruit may be masked; finish can taste metallic or bitter at high levels
Causes: contamination in winery or barrels; low SO₂; residual sugar and warm storage can favour growth. Trace Brett is debated as “terroir character” in some circles; at Level 3, treat dominant bandage/animal notes that swamp fruit as a fault when advising customers.
Out of condition
Out of condition means the wine is past its best or damaged by storage even if no single classic fault dominates.
Recognition: tired, stewed, or faded fruit; browning; loss of sparkle in sparkling wine; flat mousse; short, dull palate; sometimes seepage stains or low ullage as clues on the bottle.
Causes: excessive age for the style; heat damage; light exposure; poor logistics. A five-year-old simple rosé that tastes brown and flat is out of condition; a mature fine red with brick rim and tertiary complexity may be correctly developed—use age expectancy and style knowledge.
High SO₂
Sulfur dioxide protects wine but is unpleasant in excess.
Recognition: pungent struck-match or choking, throat-irritating sensation on the nose; sometimes a metallic or bitter edge. Recently bottled or heavily sulfited sweet wines can show this more.
Causes: heavy additions for stability (especially sweet wines, some mass-market styles); poor timing so free SO₂ remains aggressively noticeable. Swirling and brief airing may help slightly; if the sensation dominates, the bottle is faulty for service purposes.
| Fault | Key aroma/taste cues | Common causes | Service response |
|---|---|---|---|
| TCA (cork taint) | Damp cardboard, musty, muted fruit | Contaminated cork/materials | Replace bottle |
| Oxidation | Brown colour, nutty/tired, flat fruit | Oxygen, heat, poor closure | Replace; discuss storage |
| Reduction | Match → onion/rubber → rotten egg | Low O₂ winemaking/closure | Air/decant if mild; replace if severe |
| VA | Vinegar, nail varnish | Acetic bacteria + O₂ | Replace if obvious |
| Brett | Bandage, barnyard, animal | Brett yeast, low SO₂ | Replace if dominant |
| Out of condition | Tired, stewed, faded, flat mousse | Age, heat, light | Replace; advise storage |
| High SO₂ | Choking match, throat prickle | Excess SO₂ addition | Air briefly; replace if persistent |
Advising customers and writing SAQ answers
When a stem says a bottle “smells of damp cardboard,” name cork taint (TCA) and state that fruit is suppressed. When a white is brown and nutty after garage storage, link oxidation / heat damage. When a young screw-cap white smells of struck match that blows off, discuss mild reduction. Precise vocabulary scores marks; vague “it’s off” does not.
Also separate fault from personal dislike. High tannin, high acid, or strong oak are not faults. Brett at trace levels may be stylistic for some producers—but if the question describes antiseptic aromas dominating the wine, call the fault.
A newly opened bottle of white wine smells strongly of damp cardboard and the fruit aroma is almost absent. What is the most likely fault?
A young red smells of struck match and a little onion on opening, but after five minutes in a decanter the aromas become clean dark fruit. What is the best assessment?
Which pair correctly matches fault to primary cause?