Cork: The Tree the Plug

Of the approximately fifteen billion bottles of wine produced per year, twelve billion are plugged up with cork. Forty percent of this cork comes from the two million acres of cork trees in Portugal, somewhere between twenty five and thirty percent comes from Spain, and the rest comes from around the Mediterranean – France, Sardinia, Tunisia, Libya, and Morocco all produce cork. Northern California would be the perfect place to grow cork trees, and there are a few around, but it takes over forty years before the trees are mature enough to harvest cork for plugging wine bottles (they are mature enough to be harvested for other purposes after twenty five years, but wine cork takes 43 years), and that is too long. First of all, people don’t want to wait forty three years to recoup their investment. Secondly, even if they were to plant them for their grandchildren, their grandchildren would probably see more value in building condos where the cork trees once were.

In Portugal, most of the cork trees used for harvesting are wild as opposed to planted. Cork is a kind of oak tree, and Michael Pollan mentions in his interview in the Sun magazine that it is not possible to domesticate oak trees. I’m not exactly sure what he means by this – if you plant oak trees in rows do they die? Or do they just grow in weird shapes and move around so that you can’t drive by them really fast on the freeway and see straight lines?

A really big cork tree can produce 100,000 corks in a harvest, and the same tree can be harvested every nine years. This equals 11,111 corks per year. The highest grade corks go for sixty cents a pop, but only five percent of corks reach this price point. The way to get cork off a tree is with this medieval looking axe with a curved blade. The cutter swipes along the top of the cut and the bottom, then down the side before peeling off a section. The cutter must be careful not to puncture the tree, as this causes problems.

Historically, after cutting they would stack the bark in the woods and let it sit for six months. Somebody decided, however, that contact with the forest floor increased the presence of TCA, which causes cork taint. So now they put the cork straight into a factory where they slice it, plug it, sort it and ship it. They used to wash corks in chlorine, thinking that chlorine killed everything, but no, that’s not true. Chlorine may actually lead to increased presence of TCA. Instead of chlorine, they now use hydrogen peroxide.

This is why corks no longer appear perfectly white. The hydrogen peroxide is actually rather effective, as the bubble action really gets into all those cracks and holes and cleans the cork up. The cracks and holes are highly significant features on the cork. The less cracks and holes, the higher grade cork. California has the highest demand for high grade cork. This is not because Napa Cabs require a higher grade cork than Bordeaux, but because in Europe they simply produce much much more cheap wine, and therefore are in greater need of cheap cork. They’re just used to cheap cork over there. Ten years ago a high end cork would run you forty five cents and now it’s up to sixty.

The corks come to California by container ship from the Mediterranean to Houston before they get on a train. They used to ride a container ship all the way to LA or Oakland via the Panama Canal, but there was a problem there. The climate in Panama promoted mold growth, which they think increased the presence of TCA.

Normal people can detect five to six parts per trillion of TCA in a glass of white wine and ten parts per trillion in a glass of red wine. Some master tasters claim to be able to detect one part per trillion.

Nobody knows how many bottles of wine fall victim to cork taint. I’ve heard numbers up to 17%, but in my day I’ve only encountered a few. Wikipedia is not helpful on this one, as they say, “The incidence of bottles with cork taint is estimated to be between 1 and 15 percent.” One would expect that with all this new insight there’d be fewer corked bottles of wine flying around.