ubiquitous corkiness

 

A corked carrot? When taint extends far beyond wine

Jon Bonné

Sunday, April 10, 2011

The question seemed foolish, but I was with wine people at a Healdsburg restaurant and the smell was unmistakable.
"Is this apple corked?"
This particular fruit slice was in my salad, and as I passed it around - because no incidence of a corked wine (or tree fruit) is official until all wine types in the area have passed judgment - we agreed it wasn't just my nose. My apple was, indeed, corked.
To be corked, of course, is to be affected by one of several compounds, notably trichloroanisole (TCA), sometimes found in the bark of the cork oak. (For more, see sfg.ly/cVyaHu.) When that cork is used to seal a wine bottle, it can ruin the wine with a musty, wet scent often compared to wet cardboard. But TCA and sibling compounds like TBA (tribromoanisole) have a role in the larger world. Articles have been published on TCA's role in off flavors in coffee beans, for instance. Wine labs are now doing TBA analysis in such materials as cardboard packaging.
When I floated the corked-apple notion, nearly every wine person in earshot had his own tale of unexpected corkiness. Apples and celery were frequent culprits. One suggested that a certain hotel fountain was corked. I've sworn on several occasions that an ambient smell in an entryway to the San Francisco Main Library was not from its more shower-averse patrons but, in fact, from TCA. The library, I swear, was corked.
But it was the apple that made me want to investigate. How does produce in a $10 salad end up smelling like a dock warehouse?
Answers came from Christian Butzke, an associate professor of food science at Purdue University, who in addition to teaching enology has extensively studied cork taint. The picture he paints is a world full of corked scents.
"Those shaved little carrots in the bags are a great example. If you ask people about the smell - musty or moldy - they say that's just how they are," Butzke told me. "The exception becomes the rule."
Butzke had more. Fruit salads on airplanes. Clothing. He recalled traveling to South America with a man whose jacket, perhaps having gotten moldy in the closet, smelled corked. The dampness and use of chlorine bleach in front-loading washing machines is another potential culprit.
What's to blame? Nothing much different from how wine gets corked. There has to be the presence of chlorine, perhaps from a cleaning solution or even from chlorinated water. The old process for bleaching corks used a chlorine wash that was responsible for much of the taint.
There also needs to be a phenolic material, which could be anything from aroma components to tannins, usually along with cellulose (think fiber) that can harbor the taint. Put phenols together with chlorine, Butzke explained, add mold from a damp environment, and you can get TCA.
So, bagged carrots? Take a chlorinated sanitizer and the moisture inside of the plastic bags, and the presence of TCA isn't a surprise. Doubly so when you consider that vegetables often naturally have a bit of mold spore on them - especially when, like carrots, they're grown underground. (Similarly, it appears cork panels cut closest to the ground had higher incidence of TCA.)
The potential for corked produce is high enough, Butzke asserts, that many of us have become used to a low level of the cork-taint aroma all around us, perhaps mistaking it for an "earthy" taste in produce. "Really," he says, "it becomes ubiquitous in the environment."
That very concept - the environmental presence of TCA - is precisely why some notable California wineries, including Hanzell and Chateau Montelena, were dinged several years ago for the pervasive presence of taint compounds in their cellars. It's why chlorine products and chlorophenol wood preservatives are meant to be kept far from wine. (Oxygen bleaches like OxyClean are a far better bet.) And it's why one of Butzke's colleagues is using ozone to eliminate bacteria from bagged produce like, say, baby-cut carrots.
All of which hints that perhaps we've been looking at the cork-taint issue the wrong way. Certainly it has helped that the wine industry cleaned up its act, but maybe less tony produce needs scrutiny, too. Because, like corked wines, a corked apple isn't so delicious, either.

Jon Bonné is The Chronicle's wine editor. Find him at jbonne@sfchronicle.com or @jbonne on Twitter.