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Put a Cork In It

Oenophiles pop a cork and sniff it. What are they sniffing for?

I’ve never been one for cork sniffing. I always thought it was kind of a snobby thing to do, but I never really investigated the practice since I’ve never really cared much for wine. Then one day, while out for dinner with a friend, I really got into it. He ordered wine, sniffed the cork, and promptly declared the bottle unacceptable and sent it back. “Decidedly mushroomy,” he said. “Decidedly snobbery” I thought. After sniffing, he had disdainfully tossed the cork on the table from where I picked it up, ready to give it a whiff and declare that I smelled nothing. But that was not to be. The fragrance of octen-3-ol wafted into my nose. I knew this smell. I had often used a vial of it in my organic chemistry class to teach the students about smells. “Mushroom alcohol” we call this metabolite of fungi. It has a decided mushroom-like smell and the cork reeked of it.

That little adventure sent me scurrying to look into the chemistry of corks. I discovered that mushroom alcohol is the least of cork-makers’ problems. Trichloroanisole is a much bigger headache. Some ten to twelve billion corks are sold every year around the world, generating over a billion dollars in sales. Each cork costs only about 15 cents, but it has a huge responsibility. That little piece of tree bark has to protect a bottle of wine which may be worth anywhere from a few dollars to a few hundred dollars. If a cork develops an off-aroma and transfers this to the wine, the result can be economic catastrophe. And it happens. Roughly 3-8% of all corked wines develop what is known as “cork taint.”

Many compounds can contribute to the problem. The octen-3-ol I mentioned forms when small amounts of fat in the cork are broken down by microbes that have contaminated the cork. Cork comes from the bark of a tree, grown mostly in Portugal. But there is a lot of processing in-between stripping the bark and corking a bottle. Lots of opportunity for microbial infection in spite of efforts to stop it. Corks are bleached with hypochlorite, but still, there is a lot of storage and shipping involved giving microbes the opportunity to take up residence in the cork. These microbes can produce not only the mushroom smell, but even worse, they can form trichloroanisole. Wood contains naturally occurring phenols that during the chlorine bleach treatment are converted to chlorinated phenols. These in turn react with microbes to yield the smelly anisole, or “cork taint.”

What is the answer? Manufacturers have played around with all kinds of alternative sterilization techniques to protect the cork. But there is a far simpler answer. Eliminate the cork. Screw cap bottles solve the problem. But no wine lover wants to be caught unscrewing a cap. How about a plastic cork? A cork made of polyethylene has been developed and it does eliminate the cork taint problem. It looks like a real cork, pulls out like a real cork, but doesn’t smell like a real cork. Many wineries are already using polyethylene corks but the real wine snobs won’t hear of it. What do I say when they start going on about how wine needs to be naturally corked to develop the proper bouquet? Go put a cork in it. A polyethylene one.


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