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What Has Your Cork Done For You Lately?

Monday, 28 August 2006

The wine is now fully mature. Several years, if not decades, have passed since its contents have seen the outside world.  Nothing has entered the bottle; nothing has left it. The wine is now fully mature. Several years, if not decades, have passed since its contents have seen the outside world.  Nothing has entered the bottle; nothing has left it. The closure has done its job, but was it of natural cork material or synthetic?  And more importantly, how did it affect the flavor and bouquet of the wine? Although natural cork is the most widely used closure material for sealing wine bottles, it has recently come under criticism and scrutiny.  Most of the criticism about natural cork is associated with what is called cork taint, or “corkiness.”  You are at your favorite restaurant and decide to spring for a $60.00 bottle of wine. You take a whiff and all you smell is the essence of piled cardboard boxes after a rain.  The culprit, which effects between 1 to 2 percent of all bottled wines, is 2,4,6 Trichloroanisole, (abbreviated to TCA for obvious reasons) which is detectable by the human nose at 2 to 3 parts per trillion.  That is the equivalent of one drop in 21,700,000 gallons, enough to fill 1,000 average sized swimming pools. Critics of natural cork decry their use, saying that they are an antiquated closure with highly variable and unpredictable consequences.   No one in their right mind would bottle an expensive Cabernet Sauvignon with a material that may have an inherent flaw.  I believe we need to look beyond the obvious and bring this subject down to the molecular level. Cork is derived from the bark of a specific oak tree, L.–Quercus suber, grown predominantly in Portugal and Spain.  Cork bark is comprised of cells with a peculiar shape and construction.  The cells are banded together in a perfectly regular manner at the rate of 40 million cells per cubic centimeter.  This means that a standard sized cork contains almost 800 million cells!  It is interesting to note that the cells are filled with a mixture of gasses, much like the air we breathe, but without any carbon dioxide, an inert gas to wine.  Almost 90 percent of the cork’s volume consists of this “air-like” gas.  In addition, cork is only partially permeable to moisture, with a maximum water absorption of 18 percent. Regardless of the material, synthetic corks are, by definition, inert to wine.  They impart no flavor and they eliminate any possibility that the wine can come in contact with air.  Remember from high school chemistry that air is nearly 21 percent oxygen, and oxygen, in small doses, changes the chemical composition of wine over time.  This is one of the reasons we age wines in barrels so that it will soften and mellow.  This is an important concept. We have tested and tasted all combinations of wine closures and found a few startling conclusions.  First, for wines aged greater than one year in the bottle, fruit composition and wine structure were slightly greater for wines stored with natural cork than for wines stored with neutral stoppers.  For wines aged less than six months, little difference was observed; however, some synthetically sealed bottles seemed to be “flat” in aroma and flavor.  Second, wines aged for three years or more were vastly superior in aroma, bouquet, and tannin structure, as compared to synthetics.   So why is it that we see wines change with natural cork and not so with synthetics, and what IS really going on inside the bottle as it collects dust in your closet?  I have a theory that may shed some light on the issue.  Getting back to the concept that cork is of vegetable origin and predominantly air, it’s possible that as the cork starts to degrade over time the cells rupture allowing its contents (Hint: air with oxygen in it) to get into the wine.  Even the cellulous walls contain trace amounts of minerals and phenolic material.  Could it just be that the cork takes an active role in aging and developing the wine?  People who know me well know that I occasionally come up with hair-brained ideas, but hear this through.  Have you ever noticed the condition of the cork from say, a ten to twenty year old bottle of wine?  Most often it is falling apart showing loss of elasticity and a crumbly texture.  It certainly is not of the same consistency as a new cork and can be broken apart easily.   I’m sure that some part of the cellular matrix has now been destroyed.   Well, I’ve never heard or read about this theory and maybe I’ve got it all wrong.  Likely, the amount of oxygen, trace elements, and minerals contained in one small cork could not affect the whole bottle--but maybe it does.  My interest is piqued.   I think I’ll call my old college professor to see what he thinks!

 

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