Cork taint in beer and how TCA reaches bottles without corks
Cork taint is a wine word, but the compound behind it does not need a cork. It travels on damp wood, cardboard and air, then settles into beer at levels too small to measure without a laboratory.
What cork taint smells like
Cork taint smells of wet cardboard, a damp cellar or a newspaper left out in the rain. In wine it is called corked. In beer it presents as a dull, damp mustiness that strips the life out of the aroma. Hoppy beers lose their fruit. Lagers lose their clean, bready snap.
The compound behind most of it is TCA, short for 2,4,6-trichloroanisole. Sensitive tasters can pick it up at a few nanograms per litre. That is a few parts per trillion, far below anything a brewery's routine lab can measure. Confirmation needs a specialist laboratory with gas chromatography and mass spectrometry.
How TCA forms without a cork
Cork gets the blame because cork bark is a good home for the moulds that make TCA. The chemistry works anywhere the ingredients meet, though. It goes in two steps:
- Chlorine meets phenolic material, or a wood preservative or fungicide already contains chlorophenols. Either way you end up with 2,4,6-trichlorophenol (TCP).
- Moulds and some bacteria living in damp conditions convert TCP into TCA as a way of detoxifying it.
So the recipe is simple: chlorine or chlorophenols, plus damp, plus mould. Wood, cardboard and paper are perfect hosts. A brominated version of the same reaction gives TBA (2,4,6-tribromoanisole), which smells much the same and comes from brominated flame retardants and treatments.
The routes into a brewery
Once TCA or TBA forms, it travels. It is volatile enough to drift through the air of a warehouse and soak into anything porous. Brewers and wineries have traced taint to:
- Wooden pallets stored damp, particularly older ones treated with chemical preservatives.
- Cardboard cartons and dividers sitting in a humid store before packing.
- Filter sheets and filter aids stored near tainted materials.
- Crown caps and can ends kept in cartons in the same damp room.
- Wooden barrels, beams and racking cleaned with chlorine.
- Rubber hoses and seals that absorb the compound and release it slowly.
None of these touch the beer for long. They do not need to. At parts per trillion, a brief contact or a tainted atmosphere in the packaging hall is enough.
Why humid stores make it worse
Moulds need moisture. A warehouse that sits at high humidity through the monsoon, with cartons stacked against a damp wall, is close to an ideal TCA factory. Add a chlorine-based cleaner used to mop the floor or wipe wooden racking and every part of the reaction is present.
This is one reason many packaging halls now insist on plastic pallets or heat-treated wooden pallets. Pallets treated under the international ISPM 15 standard carry an HT stamp when they were heated rather than chemically treated. That does not make them immune to mould, but it removes one source of chlorophenols.
Delicate beers show it first
TCA does more than add a smell. Research in wine has shown that it suppresses other aromas, so a lightly tainted drink can simply seem dull before anyone notices a damp note. Beer behaves the same way. A pale lager at 4.5% ABV, with almost nothing to hide behind, shows taint at levels a roasty imperial stout would mask. A hazy IPA loses its fruit and nobody can say why.
That is why trained panels taste the most delicate beer in the range first when a taint is suspected. If the pale lager is clean, the packaging hall probably is too. If it seems strangely flat, the search starts with whatever that batch touched.
What drinkers can do with a tainted beer
Cork taint is rare in beer and often limited to one batch or one pallet. If a beer smells of damp cardboard:
- Smell the empty glass first, since a damp cloth can give a similar note.
- Try another bottle or can from a different pack or shop.
- Tell the brewery, with the batch code and best before date printed on the pack.
That last step helps more than you might think. A brewery cannot fix a taint it never hears about. Batch codes let it track down which pallet or carton delivery was involved. Our guide to musty and mouldy notes in beer covers the related compounds.
How breweries keep TCA out
The fixes are boring and effective. Keep chlorine away from wood. Use chlorine-free sanitisers on wooden surfaces and anywhere near packaging stores. Keep cartons, crowns and filter media in a dry room off the floor. Inspect incoming packaging by smell, because a trained nose can pick up a tainted carton batch before it reaches a bottle. Some breweries hold back a sample of each delivery of cartons or crowns for exactly this reason.
Your first step: the next time a corked wine comes your way, smell it carefully and remember it. That is the reference you need for spotting TCA in beer.
Common questions
Can beer be corked if it has a crown cap?
Yes. TCA forms wherever chlorine or chlorophenols, damp and mould meet. It can reach beer through pallets, cartons, filter sheets or the air of a damp store.
What does TCA smell like in beer?
Wet cardboard, a damp cellar or wet newspaper. It also dulls the aroma, so the beer can seem flat and lifeless.
How do brewers confirm cork taint?
TCA sits at parts per trillion, so it needs a specialist laboratory using gas chromatography and mass spectrometry. Trained tasters usually raise the alarm first.
Is TBA the same as TCA?
They are close relatives. TBA contains bromine rather than chlorine, comes from brominated treatments and flame retardants and smells much the same.
