Wines & Vines

Commonsense winemaking

Commonsense winemaking – Column

Richard G. Peterson

Q: What can restaurants and wineries do about bad corks? Restaurants can’t do anything, except to replace the occasional bottle of wine that has been spoiled and report it to the winery for replacement. Wineries have several options, although none is perfect. As long as corks are produced with present methods, we will be stuck with an average of 2-3% bad corks every year.

Recently, some cork producers have been supplying corks which were not sterilized with chlorine, but hydrogen peroxide instead. This followed the revelation that “cork taint” was identified chemically as trichloranisole (TCA), which was presumably caused by reactions between chlorine and mold residue on the cork surface. The theory was that you could stop cork taint from appearing in corks if you avoided the use of chlorine for cork sterilization. However, winemakers are now finding cork taint in batches of corks that were treated with peroxide instead of chlorind! No statistics have been accepted as yet; peroxide does seem to minimize the cork taint problem, but doesn’t completely stop it from ruining the occasional bottle of fine wine.

I’m not sure why. Since chloride occurs in all sources of water, it may be that peroxide and traces of chloride can react together with mold residue on cork raw materials to form the dreaded TCA. This, despite the fact that the cork producer doesn’t any longer use chlorine as its sterilizing agent. Can’t we attack the problem in another way? Look at the way in which corks are produced:

The bark of cork trees is removed at intervals of about nine years on any given cork oak tree. So there are about nine different layers or bark tissue in the average thickness of freshly-cut bark. The bark is “peeled” off the tree by hand, using a hatchet-like axe to remove the bark in curled sheets about 1-2 feet high by, maybe 2-3 feet wide (depends on the circumference of the tree). The chunks of fresh cork bark, called “planchets” are uncurled to flatten them and tied into bundles for drying in open air. This takes months – and a year is not unusual. After that time, the cork bark planchets are completely flat and dry, but often covered with mold. This mold is the problem.

Sure, they shave it off to expose fresh-looking cork before cutting out the wine corks from the planchet. But many areas on the surface still contain mold residue even though it isn’t visible to the naked eye. Wouldn’t it be nice to spray or dip the planchets into an indicator bath which, say, turned red wherever a spot of mold residue appeared? Then those spots could be removed before the wine-cork cutting began.

Visualize a stand of mold growing on the surface of a cork planchet. And imagine that you’re watching it at great magnification. It looks remarkably like those pictures you see in advertisements for grass seed. You see strands growing upwards from the surface and “roots” extending down into the solid surface. Lateral connectors spread out from vertical strand to vertical strand. These spread outwards like bamboo, pushing down new roots as the mass grows into ever larger patches of mold. Eventually the whole planchet is covered with mold, with the “roots” extending varying distances into the planchet.

Imagine that, when visible mold is removed (by a shaving cut just below the surface) many of the longest roots are not removed. That may or may not be important. Maybe it isn’t the roots that exude the moldy smell-more likely, the mold produces moldy flavor compounds during its growth and these diffuse into the planchet to various depths. Whichever it is, you can see that the moldy smell won’t be removed from every spot on the surface of the planchet if the shaving cut isn’t deep enough to get it all. When the cylindrical wine corks are cut from the planchet, a few of them will be cut from areas with the moldy smell even though it isn’t visible. Problem: deeper shaving wastes cork and raises the cost. Nobody wants that, so the problem continues.

Wouldn’t it be better to use a more effective fungicide to spray or paint onto the freshly-cut bark to prevent mold growth on the planchet as it dries? This might stop the mold growth on planchets altogether. Or, dry the planchets under more controlled conditions inside, rather than air-drying outside exposed to all the elements. Just an idea.

Today there is a huge amount of granular cork produced from odd shaped pieces of planchet, the skeletal remains of planchets after the wine corks have been removed and other cork odds and ends. This granular cork is “glued” together to make fishing rod handles, flooring tile, heels for shoes, etc. It can also be used to make perfectly good wine corks. Of course, wine corks have to be sealed at each end by a disk of solid cork to eliminate the possibility of crumbling. That adds expense but, still, these agglomerate corks are cheaper than single piece corks and I recommend them because they tend to have less taint. The cork producer has only to carefully select the cork disks they use for the ends. The agglomerate design has been in use for sparkling wines for decades, so it must be here to stay. Try them.

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