Secrets of Cork Testing Revealed

Aug 26, 2015

(Wines&Vines) - The problem with cork taint in wine has been well documented. By the late 1990s, an estimated 2% to 10% of wine bottles were believed to be spoiled by varying degrees of the taint, most often caused by 2,4,6-trichloroanisole (TCA). As a result, the cork industry saw some of its customers move to various alternative closures.

Clearly, something needed to be done. Peter Weber, executive director of the Cork Quality Council (CQC) in Forestville, Calif., approached Gordon Burns, co-founder and president of ETS Laboratories in St. Helena, Calif., in search of an objective way to test for TCA. 

Burns described the research Aug. 19 during the second annual Wines & Vines Packaging Conference in Napa. The ETS research allowed the company to develop a better, faster test for TCA and helped the industry understand how the level of TCA in a cork translates into the amount of taint in wine. That research also has led to better testing of corks before they leave Portugal and has allowed the CQC to develop a protocol for its members that has greatly reduced the incidence of cork taint in U.S. wines. 

A new way of testing

ETS started by hiring Eric Hervé, a chemist who was a recent Ph.D. graduate of the University of Bordeaux. The old ways of analyzing corks for TCA were laborious and not very good, Burns said, so they needed to develop a new method. “We turned Eric loose,” Burns said.

ETS had developed a technique using solid phase micro-extraction (SPME) before it was commercially available, followed by analysis with gas chromatography/mass spectroscopy (GC/MS). Hervé advanced that method, turning it into a tool that was much faster and could detect TCA below 1 part per trillion. “You’ve got to measure down to that range for it to be meaningful,” Burns said.

One key was understanding releasable TCA—the amount of TCA that is released when whole corks are soaked into wine. Hervé found that changes to the wine stop after about 24 hours. Not all TCA has migrated to the wine at that point, but an equilibrium is established, according to Burns’ presentation. “TCA likes to be in ethanol,” he said, “but it also likes to be in cork.” If you move the same cork to a fresh wine, TCA again migrates to the wine and reaches the same concentration as in the first wine, he added. 


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