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The question

Can a screw-cap wine be "corked?"

The answer

Yes, it can, though it depends on how strictly you define the term.

Contrary to almost universal belief, screw-cap wines are indeed susceptible to the sort of mouldy, off aromas typically associated with contaminated corks.

The main source of cork taint in wine is a randomly occurring chemical called 2,4,6-trichloroanisole, or TCA. It's usually produced when a fungus resident in natural cork bark comes in contact with chlorine, either during the bleaching process or when rainwater soaks into stacks of bark left to dry in the sun. It's powerful stuff and completely invisible to the eye, not to be confused with corks that are merely brittle or broken.

I'd estimate that TCA conspicuously affects at least two or three bottles in 100. And that's probably just the tip of the iceberg. At very low concentrations, even when you can't detect it directly, TCA can rob a wine of its fruity character. It's a scourge and the main reason many producers of fine wine have moved to screw caps.

But there are other, similarly mouldy contaminants closely related to TCA that have been found in wine. One of them is 2,4,6-tribromoanisole, or TBA, which has been linked to certain fungicides and wood preservatives used in the packaging industry. TBA can settle on various materials, such as wooden barrels, Styrofoam, cellar walls and wooden pallets. From there, it can migrate to polyethylene film, a plastic commonly used in screw-cap liners.

I sample a lot of wine each year and can attest to the reality of the occasional "corked" screw-cap bottle, as can many of my wine-writing colleagues. But I hasten to add that your chances of coming across such a dud is far, far lower than is the case with wines sealed under cork.

The Flavour Principle by Lucy Waverman and Beppi Crosariol (HarperCollins) won the top prize for best general English cookbook at the 2014 Taste Canada Food Writing Awards.

E-mail your wine and spirits questions to Beppi Crosariol. Look for answers to select questions to appear in the Wine & Spirits newsletter and on The Globe and Mail website.