The number most closely related to cork closures for wine bottles is three. Natural corks can taint a wine with TCA, and for most consumers it’s apparent (when measured in parts per trillion) at 3 ppm. At the wine competitions I coordinate, the percentage of TCA-tainted wines in cork-sealed bottles is also about three. At my company Riverside International, some 20,000 bottles were opened during the past decade, and we calculated that 3% were corked.

The cork industry has spent a lot of time and money countering these claims (see “Closures War at a Standstill?” in the August 2012 issue of Wines & Vines) in hopes of holding back the rising tide of synthetic closures and screwcaps. And to be sure, all of today’s alternative closures have their Achilles’ heels, most of which have been well documented (or alleged), mainly by proponents of one stripe or another.

But the main reason winemakers say they’re concerned about TCA-related problems goes beyond the likelihood that one bottle in every three cases will be tainted. Not all consumers are knowledgeable enough about wine to identify TCA’s moldy, wet cardboard-y aroma at 3 ppm. They’ll overlook the cork and instead blame the winery when they find that a wine is “off.”

Some expert tasters can detect TCA in trace amounts so small it’s probably in a concentration far less than 3 ppm. Phrases like “possibly corked” are frequently heard from professional wine judges. Re-tastes of second bottles usually prove something was wrong. One theory: It might have been TCA taint at below the 3 ppm threshold. In that case, could cork taint at those levels be as much as 9%-10%?

Random oxidation
To conclude that cork is at fault is a leap of anti-faith in natural cork, which has a long if not always proud history of closing wine bottles. Indeed, random oxidation in wine occasionally has been accused of being cork taint, even when it has nothing to do with the cork.

If a bottle is manufactured improperly and the neck tolerances are faulty, corks may not properly seal, allowing oxygen to reach the wine. Though this has nothing to do with TCA, some amateur tasters will make that assumption, and the cork producer will be tarred with an unlikely brush—improperly made bottles. In such cases, an entire batch of wine could be scarred.

Also, random oxidation could come from a simply ratty cork. Cork, a natural product, is subject to variations; a creased cork can allow air in, creating oxidation.

What do you get when the bottling line is old or works inefficiently in removing the oxygen from the headspace in a bottleneck? What if the bottling line fails to add the right amount of inert gas? The result: Air gets into the headspace, and the wine begins to oxidize more rapidly than it should. Again, this has nothing to do with corks.

Screwcaps appear to be a solution to TCA infection. Since much of Australia and almost all of New Zealand have switched over to caps, we’ve seen almost no wine bottles infected for TCA.

Mistaken smells
Of course, non-professionals can cause havoc here if they mistake the “skunky” smell in screwcapped wine with TCA. That skunky aroma is likely reduction caused by a “bad” bottle. Screwcaps show up most on early-drinking wines, most of which are white. A large percentage of such bottles are clear (flint) and have no ultra-violet protectant in the glass. Such wines can get reduced if hit by direct light.

This “lightstruck” character has nothing to do with TCA, but again non-professionals can create headaches here.

How are screwcaps doing? Rather well. After an initial period when restaurant wine service personnel were opposed to them (they supposedly eliminated the ritual opening of the bottle and the ritual taste pour), most have embraced screwcaps since they have all but eliminated accusations that a wine is corked when, in fact, it was not.

I’m certain I’ll never see a First Growth Bordeaux with a screwcap, but one of Australia’s greatest red wines, the superb Shiraz Giaconda from winemaker Rick Kinzbrunner, sells for about $70 per bottle with a choice of either cork- or screwcap-sealed bottles.

As years go by, the screwcap will either be proved to have great value in dealing with TCA or be seen as a false solution. I’m betting on the former.

Dan Berger has been a wine columnist since 1976. Currently he issues weekly wine commentary, Dan Berger’s Vintage Experiences, and a nationally syndicated wine column. He also coordinates the Riverside International Wine Competition.