The Stopping Power of Quercus Suber

I have to admit I’m still rather intimidated by a corkscrew.  I’ve tried every gadget on the market to get a cork out smoothly and professionally.  There is a definite etiquette about getting a cork out of a wine bottle; I’ve learned that by pouring wine at different events and sniffing the corks at expensive restaurants.  But I’ve also had to pick out bits of cork floating in a wine glass, and I’ve created a few spectacular wine geysers by pushing the cork inside the bottle.  So why use a cork?

Corks have been used for centuries to keep the wine in and the oxygen out.   Many winemakers have told me they get the best seal with a screw top, but the wine drinking public isn’t quite ready for that.  However cork is getting expensive to use; you may have seen some corks made from cork mash with a thin veneer of cork around the outside, or synthetic corks that are a rubbery resin material.  So what’s the difference?  And does the cork tell you anything about the wine inside?

Corks were first used by the Greeks and Romans.  The wine was kept in clay amphora jars and sealed with cork when available. This early cork seal was not very tight and wine went bad quickly. The other method the Greeks and Romans used to seal the jars was to use wax or resin. In order to open them the top had to be scraped off, which made resealing them very difficult.  In medieval times wood stoppers were used, but they had the same problems with leakage.

It wasn’t until the 17th century that the concept of the cork and corkscrew was developed, and that development was based on the shape of the container changing from a jar to a long necked glass bottle. The light and clean properties of the bark on the cork oak tree were very appealing to winemakers. It was also available in mass quantities and fairly easy to manufacture.
Cork comes from the cork tree, or Quercus Suber. This is a species of oak that grows in Spain and Portugal. The older the tree, the more cork it produces.  Cork naturally grows to form 14-sided cells in the bark. Strips are carefully removed and dried in strips for 6 months.  The strips are then boiled and dried for another 3 weeks.  The cork strips are cut into the round cylinders we are familiar with.  Only 40% of this final cut ends up being usable.
Cork does not go brittle or rotten for a long time after it is in a bottle. Some corks have been known to keep a good seal for 100 years, and if the seal is good the wine inside had a good chance of having a long shelf life in your wine rack.  There are different grades of cork, and often the best corks are kept for the best wines.
Synthetic corks are much cheaper than cork or even composite cork mash stoppers.  These stoppers are made from a unique formulation that creates a dual density foam core. A uniform skin with the balance of compressibility and memory provides a proper seal with no leakage or bacteria holding properties. The compressibility and memory are created by a very fine cell structure next to the outer skin that becomes less dense toward the center.  Synthetic corks are being used in Canada, California, Australia and South Africa.
One good thing about synthetic corks is that they are bacteria free, and that solves one of the biggest problems with corks…Corking.  When you smell a cork and look at the bottle end of a cork you are looking for mold that can occur in the cork itself.  This bacterium spoils the wine, making it undrinkable. If you see mold on the cork in a restaurant or on a cork at home send it or take it back.  Synthetics also have a tighter seal and that means a longer shelf life and not much evaporation.
The day is coming when you may not need to sniff another cork, and if the industry moves towards screw tops corkscrews may become obsolete.  But ritual is still a part of the wine experience, and nothing pops quite like an authentic cork coming out of a good bottle of wine!


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