How to tell if a bottle is corked?

Detecting a corked bottle? It’s simple! Just take the cork from the bottle you’ve just opened and smell the part that was in contact with the wine.

If it has a slight cork smell, the bottle is likely corked. You can also pour the wine into a glass and smell or even taste it, as these methods can also help identify cork taint.

Why is a bottle corked?

The corks are made from tree bark. If the tree is affected by a disease, it also impacts the cork and, consequently, the bottle it’s in.

What is TCA, the molecule behind corked wine?

TCA, or 2,4,6-trichloroanisole, is the main molecule that makes a wine corked: it smells musty and switches off the aromas. It is not so much the tree that is sick as its bark that has been contaminated: TCA forms in the cork when moulds transform chlorinated compounds called chlorophenols.

The chlorine comes from bark polluted by insecticides, or from chlorinated products long used in cellars and to bleach cork. The nose picks it up at tiny doses: 1.5 to 5 nanograms per litre according to the French Vine and Wine Institute (IFV), a few billionths of a gram.

Which smells give away a corked bottle?

Wet cardboard, damp cellar, mould, wet dog: the smells of a corked bottle. At a high dose you cannot miss them. At a low dose, none of that: the wine just seems muted, fruitless and short, as if someone had turned the volume down.

Japanese researchers showed in 2013 that TCA blocks olfactory signals: it does not just add a bad smell, it stops you smelling the rest. Muffled fruit or outright mould, it comes down to dose; tasters catch it sooner in a dry white wine.

When in doubt, leave the glass ten minutes: cork taint grows with air, it does not blow off.

What gets mistaken for cork taint?

Four faults and a merely closed wine imitate cork taint. The referee is air: TCA's mustiness resists it, most other smells shift.

Reduction, a wine starved of air: egg, struck match, rubber; ten minutes in a decanter and they fade. Oxidation, the opposite, too much air: bruised apple, walnut, Madeira, a browning colour, never wet cardboard.

Brettanomyces, an unwanted yeast, mostly in full-bodied reds: stable, leather, animal rather than cellar. Volatile acidity: vinegar, nail varnish, a sting. A closed wine: almost silent, but nothing bad; an hour in a decanter wakes it, which a corked wine never will.

Does a cork that smells of cork mean the wine is corked?

Not necessarily: natural cork smells of cork, and that smell alone says nothing about the wine. The useful signal is mould or wet cardboard on the end that touched the wine.

A perfect-looking cork may have passed its TCA into the wine. Conversely, a cork stained or mouldy on the capsule side has often passed on nothing: that end never met the wine. Sniffing it is a first clue, never a verdict.

The real judge is the glass: if the nose says damp cellar and the fruit has gone, the bottle is corked, whatever the cork looks like.

Does cling film save a corked wine?

Partly, and under experimental conditions. Bordeaux researchers tested the trick in 2020: after eight hours in the wine, a film had absorbed about half the TCA, over 80% after two days.

They used a specific food-grade film, not the kitchen roll. The plastic also takes up a few esters, the compounds behind the fruit, even though the treated wines seemed fruitier once the TCA was gone. At home it is a gamble on a lost bottle.

No curative treatment is authorised for producers anyway, the IFV points out. And do not count on cooking: what spoils the glass spoils the dish.

What should you do at a restaurant or after a purchase?

Say so, calmly and at once. At a restaurant, tell the sommelier or waiter at the first glass, without making a scene. Cork taint is nobody's fault at the table, and the house replaces the bottle.

From a wine shop or online, recork the bottle, keep it with its cork and tell the seller promptly: that is what they will want to confirm the fault. A photo of the label helps.

On Avenue des Vins, every bottle ships from the winemaker's cellar and the winemaker is your contact: our customer service passes on your claim, and they settle the next step with you.

How many bottles are corked, and how do producers protect themselves?

Between 1 and 5% of bottles by the usual estimates, more according to a few older sources. In Bordeaux, an eleven-year survey by the trade body found 2.38% of wines judged corked, and falling.

Producers have several defences. Technical corks, agglomerated cork cleaned of its odorous molecules, were under 1% of faults in that survey. Synthetic corks and screw caps remove the cork and its TCA, without shielding against contamination from the cellar.

Glass stoppers play the same card. Cellars have changed too: chlorine has all but disappeared from them, treated wood is getting rare, and batches of corks are analysed before bottling.

FAQ - Spotting a corked bottle

Can a champagne be corked?

Yes. A champagne cork is made of cork: an agglomerated body and, on the wine side, two discs of natural cork, precisely the part that touches the wine. TCA can settle there as in any classic cork. The bubbles change nothing: damp-cellar nose, missing fruit, short finish, same diagnosis.

Can everyone smell cork taint?

No, far from it. Sensitivity to TCA varies enormously: some tasters catch it at one or two nanograms per litre, others need a hundred to two hundred times more. Hence the arguments over one bottle. Training sharpens the nose: the more often you meet this fault, the faster you spot it. A matter of threshold, not taste.

Is an older wine more likely to be corked?

Slightly, yes. TCA migrates slowly from cork into wine: a bottle clean at bottling can turn out corked years later, and the risk grows with the years. A lottery, cork by cork: in the same case of six, one bottle can be spoiled and the other five perfect.

Is a corked wine the winemaker's fault?

No, in the vast majority of cases. The cork brings the TCA in 95% of contaminations, and the winemaker buys it in: they can have a batch analysed or ask for a certificate, but not sniff every cork before bottling. Report it without embarrassment: they would rather know, if only to change supplier.

Why are you asked to taste the wine at a restaurant?

To check it has no fault, not to see if you like it. The ritual catches cork taint or an oxidised wine before the table is served. Smell first, then taste, take your time: refusing a bottle is nothing to be awkward about, but the reason must be a fault, not a disappointment.