The Real Problem With Corks

Aussie researchers focus on bottle variation
Mar 9, 2010

Too much of the discussion of corks vs. alternative closures centers on cork taint. That is only part of the problem. The sneakiest, most worrisome issue is how every bottle in a case of cork-finished wines often ages into something different. A 10-year scientific study from Australia, recently concluded, shines a spotlight on that, almost literally.

Photographs (see below, screw-capped wines at far left) from a 10-year study undertaken by the Australian Wine Research Institute (AWRI) vividly show what happens to a good wine under different closures over time. The trial used thousands of bottles of a 1999 Clare Sémillon made at Leasingham and sealed with 14 different closures. Once a year, researchers opened, analyzed and sampled the wines in the lab.

The fresh-looking bottle on the left of each photograph is the one sealed by a screwcap. All of the others show varying degrees of oxidation. After a decade, the wines sealed under screw cap were still drinkable and showed appealing secondary aged characters while retaining freshness in the blind tastings.

And yet, there are those who still believe that wines won’t age under screw caps.

When the study began, it was not to test screw caps, but to see how wines developed under corks. “[We wanted] to determine which would be the best performing cork and we didn’t expect screw cap to be much of a factor,” said Peter Godden, group manager at the AWRI. “It didn’t take long to work out that it was going to be the most reliable performer and, as it turns out, the results are emphatic.”

How good was the wine? “The wine under screw cap was classic aged Sémillon and was wonderful to drink,” Godden said. He added that there was huge variation in the results for the synthetic and cork closures, which he found to be of greater concern than TCA taint.

“Most of the wine sealed with closures other than screw cap were completely undrinkable.” That would include corks.

This is why I am such an unabashed fan of screw caps. For my money, the sooner every bottle is sealed with them, the better. Australia is on the bandwagon. Twist-offs seal more than half the wines I taste from Oz now, and the percentage grows every year. I love it.

Until the advent of twists, those who like aged wines could only shrug and accept bottle variation as a given. We expect it from wines sealed under cork. One bottle might be fresh and complex, the next a bit muted by oxidation, another badly oxidized, and probably one ruined by cork taint (aka TCA). And then there are the ones in between, where TCA (or some other microscopic taint from the cork) takes enough of the edge off a wine for it to show poorly. That happens more often, in my experience, than full-blown corkiness.

Are twist-offs perfect? Not quite, but the down sides are manageable, while cork problems occur indiscriminately and exponentially more often. Winemaking for screw-cap closures needs to be clean, and sulfur must be handled carefully to avoid reduction. Aging occurs at a slower pace under screw caps (actually, at about the same pace as the rare perfect cork), so if you like those complex flavors of older wine, it will take longer to achieve them. But they do arrive, and the original fruit remains.

Long ago I got over missing the sound of the cork popping. The satisfaction of the wine in the glass being what the winemaker intended more than makes up for that.

Most of all, I love the peace of mind that twist-offs ensure. I have screw-capped wines in my cellar that date from the late 1990s. Every one of them has developed beautifully. To this date, none has gone over the hill, and I never have to worry about a bad cork. Bliss.

Courtesy: Australian Wine Research Institute
Closures Screwcaps

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