Have you ever popped open the cork from a bottle of wine, poured the wine into your stemware, only to detect a “funky” odor; perhaps the scent of wet newspaper or mold?  Some people refer to this as “corked” wine.  Occasionally and perhaps more often than we would like to acknowledge, we come face with face, or perhaps I should say nose to nose with that scenario.  Sometimes the odor is blatantly offensive, the stench of mold overwhelming the wine’s natural aromas.  But more often, it’s weaved within the character of the wine which can range from an “unenthusiastic” listless wine to one with a wet and earthy fragrance.   

One of the most common underlying causes of stale smelling corked wine is the tainting of the cork by the chemical TCA or 2,4,6- trichloroanisole.  The compound is formed by interactions between plant phenols, mold and chlorine (cleanser) and can impart a musty, moldy aroma to the wine itself.  If wood “carriers” are present in the vicinity of the TCA ingredients, carriers such as pallets, oak barrels, wood walls and beams, TCA can form on them as well.  Just imagine the scent of a wine aging inside of a TCA tainted barrel.  Transfer this to the bottles and you have potentially over two hundred TCA “infected” bottles of wine.

As you might imagine, TCA can spread quite readily, infecting a large portion of a winery and causing the facility to call in large volumes of wine while canceling the distribution of others.  The results can be financially catastrophic, especially if you’re a small winery.  Over the last several years, a number of domestic and international wineries have been challenged with TCA, so the issue is real and widespread.  TCA is measured in ng/L or ppt (parts per trillion) through a sophisticated testing process that I will leave to the chemists.  Suffice it to say, TCA levels can be measured with great accuracy.

How can you be certain that the wine you are tasting is tainted with TCA?  You may never be absolutely certain unless you measure TCA levels.  First, you need to rule out alternative causes of wine damage such as heat and oxidation from a faulty cork.  With these ruled out, it become more suspicious that TCA is the cause.  As well, both the concentration of TCA and the sensitivity of the taster come into play.

The average human perception threshold to TCA seems to lie around 5-10 ppt (parts per trillion) but sensitivity is variable from one individual to another, possibly a function of genetics and wine tasting experience.  Some tasters can identify the “off” TCA aromas at only 1-2 ppt.  While the aromas certainly can be offensive, the good news is that there is no health risk to imbibing TCA tainted wine.

The statistical frequency of TCA tainted wines differs according to whether you’re a professional tester, a novice or a member of the cork industry.  Professional wine publications such as The Wine Spectator claim that, based upon its tastings of thousands of wines, the incidence approaches 15%.  The 2004 Wine Spectator California Wine Experience group of sommeliers reported a 4-12% incidence of “corked” wines.  So, it’s probably a safe bet that the incidence lies around 10%, give or take. 

So the big question is, is that an issue for you and me as a consumer?  I think it is.  No one is happy about feeding their newly opened bottle of wine to the sink, even more irritating if the bottle is a pricey one.  To put this into a perspective, the statistics say that if you have a collection (any price) of wine totaling 100 bottles, 10 on average are likely to be tainted with TCA.  So what can be done?

Once a bottle is sealed at the winery, there is nothing, as a consumer, that you can do to remove the unfavorable tastes and aromas.  Certainly if you believe that the bottle is tainted and corky, reseal it and request that the retailer or sommelier sample the wine to confirm you suspicions.  Chances are good that the bottle will be replaced, especially if the corky scent is obvious.  From a producer standpoint, there are a few options available to reduce or even eliminate the offensive TCA odors.  The most effective, thus far, is to seal the bottle with a screw cap in place of cork.  To my knowledge (and in my tasting experience), screw caps eliminate the issue, for all practical purposes.  The metal cap does not serve as a medium for the development of TCA. 

Another useful and effective strategy is for the producer to routinely clean his facility and test for TCA.  If TCA is discovered early, he or she can take immediate action to reduce the risks of the taint spreading.  While TCA is a strong culprit for corkiness, a “relative” called TBA (tribromoanisole) may also be the culprit, the cause identified as the microbial degradation by fungi of tribromophenol or TBP used in wood preservatives or as a flame retardant in paint and plastics.  In this case, the cork only acts as a “carrier” of the taint.  Thus far, it is not possible to distinguish TCA from TBA by taste.