The perfect closure: getting closer – chemicals in natural cork wine closures

Larry Walker

Very few wine issues have polarized the wine trade the way closures have in the past few years. Defenders of cork have sometimes become a bit emotional in defending the product against those offering synthetic closures or screwcaps. Last year, APCOR, the Portuguese Cork Association, began a 2.5 million euro program to fund research with the objective of eradicating TCA in natural cork wine closures.

(TCA or 2, 4, 6-trichloroanisole, is a naturally occurring, odorous but harmless compound that certain microorganisms produce in the presence of chlorine. This chemical has been known to be a spoilage compound in natural corks.)

As detailed in our Sept., 2002 cover story about the Portuguese cork industry, APCOR’s research will cover five areas of critical interest to the wine trade, including investigating the lifecycle of natural cork stoppers, the stabilization period of raw natural cork and natural cork’s contribution to the maturation of wine. On top of this, APCOR will also be conducting tests on new treatments and developments within the cork industry and new processes with the sole aim of eradicating TCA.

Francisco de Brito Evangelista, the director for APCOR’s International Campaign for Cork, stated, “This initiative is a breakthrough for our industry. It demonstrates clearly, and for the first time, that we are dedicating the appropriate resources to finding a solution to TCA in natural cork stoppers–industry-wide.”

In January, Amorim Cork America, a division of Grupo Amorim, the world’s largest producer of natural cork closures, announced laboratory findings confirming a further 60% reduction in TCA levels in the company’s natural cork closures. These results were validated over a two-year period since the inception of Amorim’s gas chromatography/mass spectroscopy screening by ETS Laboratories in Napa.

According to an Amorim statement, the recent decrease in TCA is a direct result of a $6 million research and development department founded in 1999. Another key to the TCA reduction is a proprietary cleaning system called CONVEX (Continuous Volatile Extractor) in place at the company’s processing plants in Ponte de Sor and Coruche, Portugal.

“As the industry leader, Amorim has been working very hard to achieve a consistent and sustainable reduction in TCA levels over the years,” said Daryl Eklund, general manager of Amorim Cork America in a statement. “TCA in Amorim corks has always been low and, in most cases, absent. But since we’ve begun receiving corks from our state-of-the-art Ponte de Sor and Coruche plants, we’ve documented an additional drop in TCA levels. Obviously, we are very happy to see this reduction validated by ETS Laboratories, but we also know that even greater advances are required. Because of Amorim’s commitment to R&D and our unique technological edge, I am confident we will see further reductions in the future.”

On the other hand, New Zealand producers who are using screwtops for closures claim a global surge in demand. Auckland-based Kim Crawford Wines and Marlborough’s Lawsons Dry Hills Wines have switched entirely to screwcaps for their 2002 wines, including export wines destined for the United Kingdom, United States and Australia. Lawsons is also using screwcaps for 100% of its deliveries to Ireland, Denmark, Belgium, Hong Kong and Singapore.

Forrest Estate Winery in Marlborough on New Zealand’s South Island bottled 50% of this year’s exports in screwcaps, including 100% of its deliveries to the U.S. and Australia. Forrest and Lawsons use exclusively screwcapped wines for the New Zealand domestic market.

All three producers maintain that screwtops help emphasize their wines’ intensely fruity flavors by eliminating cork taint and minimizing oxidation. They also credit screwcaps with sealing-in consistency and with allowing slow, even aging of wine.

“We were always confident that screwcapped wine would be accepted by a large percentage of consumers,” said Erica Crawford, executive director of Kim Crawford Wines. “Even so, we’ve been amazed by the popularity of the new closures in just about every market.” Kim Crawford was the first New Zealand winery to release a screwcap wine in August, 2001.

According to Crawford, the winery has been particularly surprised by the success of screwcaps in the U.S. She believes the new packaging gives the winery an “extra edge” as innovators in the competitive U.S. market, where consumers seem to be more interested in the quality of the wine than in the ceremony and mystique traditionally associated with corks.

Just what percentage of wine is corked is at the heart of the debate. The number is commonly reported at between 2% and 5%. Last year, the Wine & Spirit Association (a UK group) reported the final results of a UK survey of nearly 14,000 bottles of wine. The survey was launched in 2001, using results from British supermarkets in an effort to determine what the percentage of corked wines really is. The idea was that whenever a retailer opened a bottle of wine to sample, it should be tasted for cork taint. In the end, 13,780 bottles were tested, with cork taint affecting just 0.7% of the bottles. More of the bottles (1%-plus) were affected by oxidation than cork taint.

Along those lines, Randall Grahm, who has switched from cork to artificial closures to screwcaps at Bonny Doon Vineyards, told Harpers Wine & Spirits Weekly in London that he stopped using artificial closures because of problems with oxidation. The trouble he found was that the synthetic closures were causing the wines to age prematurely because of a rapid drop in sulfur dioxide levels in the bottle.

On the other hand, yellow tail (sic), the No. 1 imported wine brand in the U.S. for almost two years, has had great success with its NuKorc synthetic stoppers.

Wines & Vines conducted an informal survey regarding closures at the Unified Wine & Grape tradeshow in January. We asked winemakers and winery owners who visited the Wines & Vines booth what closures they are currently using, if they were happy with that closure or if they were thinking of trying something different.

Of those who responded, 73% reported they were using cork closures and 93% of them were happy with the corks. Some 22% were using synthetic closures and 90% were happy with the closures. The remaining 5% were using screwcaps and were 100% happy with that choice.

Of those not happy with cork closures, most cited fear of TCA contamination, although several were also interested in finding an alternative closure for lower-priced wines in their portfolio. Those unhappy with synthetic closures mentioned the difficulty in extracting the closures or fears of premature oxidation.

This survey was admittedly small and limited to those who attended Unified, stopped at the Wines & Vines booth and had the time to answer our questions. In the interest of shedding some light on the closure question, Wines & Vines would be glad to hear from winemakers, production managers and winery owners on the subject. Perhaps in a future issue, we could revisit the question of closures with additional input from the winemaking community. Please send your comments by email to:

COPYRIGHT 2003 Hiaring Company

COPYRIGHT 2003 Gale Group

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