[Photo courtesy Amorim]

Cork has been the most preferred closure for wine bottles since its initial use in the mid-16th century (especially since, before cork, the alternatives were oil-soaked cloth or some sort of resin-coated lid). Wineries used it pretty much without question for 300 years. And why not? It came from a renewable resource, it was pliable, and it could be used to re-seal bottles. While it took a while for some technology (such as the corkscrew) to catch up, cork closures also proved to be a big hit with consumers. There’s no sound quite like that of a cork coming out of a bottle. The use of corks for wine bottles seemed like a beautiful pairing.

Most cork used in the beverage industry globally comes from sustainably farmed forests in Portugal, and Associação Portuguesa da Cortiça (aka the Portuguese Cork Association, or APCOR) has considerable amounts of data about the widespread use, acceptance, and even preference for cork. Its research shows 93 percent of consumers link a cork closure with quality. With 70 percent of all wine stoppers made from cork, that translates into something on the order of 12 billion corks per year.


The Rise of TCA

In the 1970s, some wineries (mostly outside of Europe) began noticing a problem with their wines that were laid down to age in bottle for several years: a new and very undesirable bouquet—the smell of a dark, dank basement. After some investigation, the culprit was identified as 2,4,6-trichloroanisole (TCA, for short), which was found to be coming from the corks.

Further investigation revealed chlorine-based agents used in processing some corks left behind residual compounds that would interact with the wine (or beer, spirits, or cider) during prolonged bottle aging and produce the offending aroma. TCA would overwhelm both the smell and taste of the product to the point it lacked any of its expected characteristics, be it berry, tree fruit, malty, hoppy, or any other pleasing notes. While TCA doesn’t pose any health issue, the unpleasantness of the experience caused great consternation in the industry. (In recent years, producers have been phasing chlorine-based agents out of cork processing.)

The most boisterous complaints initially came from Australian and California wineries, but others soon joined the chorus. Then complaints started to come from others around the world.

While in some instances, whole lots of wine would be tainted with TCA, more often than not the effect would vary from bottle to bottle. In the early 2000s, APCOR estimated the cork taint rate between 0.7 and 1.2 percent, while a 2005 Wine Spectator blind tasting set the figure as high as 7 percent (out of 2,800 bottles randomly sampled, that would be one bottle per case, on average). By 2013, the Cork Quality Council (a U.S.-based nonprofit founded to promote education and improve quality assurance performance for the wine and cork industries) estimated the rate to be a mere fraction of these earlier studies. But for producers, even one tainted bottle was too many.

Bottom line: TCA was a serious problem, and the cork industry had to find a solution.


The automated process uses gas phase spectroscopy, leaving no “margin of human subjectivity.” —Neil Foster, M.A. Silva

Improved testing methods

Solving TCA was important not just to keep cork-using producers happy, but because of new market competition. By the latter part of the 20th century, screwcaps had started to gain a foothold in the wine industry, and synthetic, cork-shaped closures were coming on the market as well. With growing consumer acceptance of these alternatives, the cork industry had to act quickly to improve processing methods and quality control before corks left the plant. It also needed to be able to show hard scientific results to regain the trust of its customers.

Today, the cork industry employs computer-aided TCA-detection processes to inspect cork on a molecular level to ensure purity. For example, Lafitte Cork & Capsule’s Electvs System analyzes each cork going through processing, adding sensory analysis and independent GCMS (gas chromatography–mass spectrometry) analysis for TCA. The company lists CEVAQOE in Portugal and ETS labs in California as using solid-phase micro extraction (SPME) testing on Lafitte corks as well.

M.A. Silva’s new onebyone system inspects each cork for any trace of TCA. The automated process uses gas phase spectroscopy, leaving no “margin of human subjectivity,” says Neil Foster, President of M.A. Silva USA. If the analysis detects TCA, the cork is rejected. This testing method is the latest innovation of M.A. Silva’s commitment to provide TCA-free corks.

Using a technology it calls NDtech (again, computer-controlled testing with chromatography), Amorim Cork guarantees any cork with more than 0.5 nanograms of TCA per litre (parts per trillion) will be automatically rejected. According to Director of Sales and Marketing Vance Rose, Amorim sells more than 4.5 billion corks per year. “All of the corks that carry the NDtech name are guaranteed to be individually tested. The company also has a more economical line of technical corks, called Neutrocork Premium, that are guaranteed to have no measurable TCA (.5 PPT being the threshold of quantifiability).”

“The new system will eliminate the risk of TCA in natural cork at levels as low as 1 part per trillion.” —Greg Hirson, Cork Supply

In 2009, Cork Supply began developing a first-of-its-kind “dry soak” system, called DS100, to detect and eliminate corks with releasable TCA at levels far below the sensory threshold. The system was introduced to customers in 2013, and it’s now used to evaluate more than 6 million corks per year. In May 2016, Cork Supply introduced DS100+, a faster, automated service with new, state-of-the-art equipment that offers 100 percent taint-free corks of any size to an even wider range of customers. “The new system will eliminate the risk of TCA in natural cork at levels as low as 1 part per trillion,” says Greg Hirson, technical director with Cork Supply.

This micro level of detection—examining each cork separately—isn’t available for every cork at every price level. Individual cork testing comes with added cost, sometimes as much as $2 (or more) per cork. All batches of corks are tested to some degree (even if it’s a random sample per batch), and hopefully, as these advanced testing techniques are refined and as technology improves, more and more beverage producers will have access to corks that have undergone these types of deep screenings.

Going forward, the cork industry needs to stay vigilant in its processing and testing methods. And remember: Older bottles may still have cork taint issues when they’re finally opened. However, given commitment of cork manufacturers to detect and eliminate TCA, the resulting improvements can only mean higher quality for everyone.



(Author’s note: During the writing of this piece, Cayuse Vineyards announced that some of its 2015 vintage wines would not be released due to paraffin particulate that separated from cork and mingled with the wine. The announcement prompted many questions about the nature of the contamination, but this isn’t a case of TCA.)