What is cork taint (TCA)?
Quick answer
Cork taint is that damp cardboard, musty basement smell that ruins an otherwise good bottle. It is caused by a molecule called TCA (2,4,6-trichloroanisole), which forms when mould in the cork reacts with chlorine-based cleaning products. About 2-5% of cork-sealed bottles are affected, and there is no way to fix it once it is there.
Detailed answer
Cork taint is the wine world's most common and most heartbreaking fault. You have been saving a special bottle for years, you pull the cork with anticipation, and... wet newspaper. Here is exactly what is going on.
The culprit is a molecule called 2,4,6-trichloroanisole, or TCA for short. It forms when naturally occurring fungi in the bark of cork oak trees come into contact with chlorophenols -- chemicals that used to be widely used to bleach and sanitise corks. The fungi convert these chlorophenols into TCA, which is detectable at insanely low concentrations: 2-4 nanograms per litre. That is roughly equivalent to one drop in 800 Olympic swimming pools.
At very low levels, TCA does not make wine smell obviously musty. Instead, it 'scalps' the fruit aromas, making the wine taste flat, muted, and lifeless. Many people drink subtly corked wine without realising it -- they just think the wine is boring. At higher concentrations, the classic damp cardboard, mouldy basement, and wet dog smells become unmistakable.
The cork industry has fought back hard. Modern treatments like Amorim's ROSA process (steaming individual corks) and Diam's supercritical CO₂ extraction have slashed contamination rates from around 8% in the 1990s to 2-3% today. Individual cork testing using gas chromatography is now possible but adds cost.
Alternatives to natural cork -- screw caps, synthetic corks, glass stoppers -- eliminate TCA risk entirely but come with trade-offs in terms of oxygen ingress and ageing potential. The debate between cork purists and screw-cap advocates is one of wine's most passionate.
If you suspect a bottle is corked, pour a small amount and wait 10 minutes -- TCA intensifies with air exposure. If confirmed, the wine cannot be saved. Any reputable wine shop (including expertvin.be) will accept the return.
| TCA level | Concentration | Effect on wine |
|---|---|---|
| Below threshold | < 1.5 ng/L | No perceptible effect |
| Subtle (scalping) | 1.5 – 4 ng/L | Fruit loss, flat wine |
| Moderate | 4 – 10 ng/L | Wet cardboard noticeable |
| Pronounced | 10 – 50 ng/L | Obvious mould, undrinkable |
| Severe | > 50 ng/L | Dominant damp cellar smell |