ISO 20752:2023 - Cork Stoppers | TCA Release Testing

Have you opened a bottle of wine and been hit with a musty, moldy smell—like wet newspaper or a damp basement? Chances are, your wine was “corked,” or tainted by 2,4,6-trichloroanisole (TCA): a compound that causes those unpleasant aromas even at extremely low concentrations. While some wine flaws can be subjective, cork taint is always a flaw at any detectable level. ISO 20752:2023—Cork stoppers – Determination of releasable 2,4,6-trichloroanisol (TCA) provides a reliable method for measuring TCA levels in cork stoppers, helping wineries prevent cork taint and ensure better wine quality.

What Is TCA (2,4,6-trichloroanisole)?

TCA stands for 2,4,6-trichloroanisole, a chemical compound so powerful that even in infinitesimal amounts it can cause musty, moldy aromas and flavors in wines. By altering the wine’s aroma and taste, TCA causes that undesirable cork taint.

How Much Wine Is Affected by TCA (Cork Taint)?

About 2-3% of wines closed with natural cork are affected by TCA (cork taint), though estimates vary, with some tasting panels finding 3.5-6% tainted—leading to potentially billions of bottles ruined annually. The cork industry, however, has made significant improvements reducing rates over time.

How Is Cork Taint Caused?

TCA is formed when naturally occurring fungi in cork, wood, or certain bacteria react with chlorinated compounds (from cleaners, pesticides) or wood preservatives, transferring them into TCA. These precursors (chlorophenols) can come from industrial sources, pesticides (like those used in cork forests), or even chlorine-based cleaners in wineries, leading to the unpleasant musty smell in wine.

Luckily, ISO 20752:2023 provides a standardized way for the wine and cork industries to assess cork quality and prevent TCA contamination, protecting wine integrity.

What Is ISO 20752:2023?

ISO 20752:2023 specifies a test method to determine releasable 2,4,6-trichloroanisole (TCA) from all types of cork stoppers and their constituents. This international standard aims to quantify how much TCA can migrate from a cork stopper into a liquid, simulating what happens in a wine bottle, and it offers a reliable procedure for preventing the contamination that can compromise wine’s flavor and aroma.

Preventing Cork Taint

Winemakers utilize a variety of techniques, such as those detailed in ISO 20752:2023, to try and minimize the presence of cork taint. This can include testing individual corks for the presence of TSA and/or soaking a selection of corks from each bale in a neutral alcohol solution and then smelling each to look for TCA. If winemakers find a contaminated cork in a sampling, they reject the entire bale.

How to Detect Cork Taint as a Consumer

Once a wine is contaminated by TCA, it will remain contaminated. As a consumer, you can detect cork taint (TCA) by swirling your wine in the glass and taking a deep sniff. If the aroma is muted or unpleasantly earthy, the wine is likely corked. Professional wine testers may use gas chromatography or other lab methods to measure TCA levels, but for the average wine drinker, a strong musty scent is the easiest and most reliable indicator.