Cork makes for an unbeatable bottle stopper. Cork’s been doing the same job well for thousands of years. Ceramics with cork tops were tucked into Egyptian tombs, and the Greeks shoved the spongy wood in containers filled with wine and olive oil.
The actual cork substance comes from Quercus suber, commonly called the Cork Oak, a medium-sized, evergreen oak tree that can live to be over 200 years old. The tree is native to southwest Europe and northwest Africa, where there are over 6 million acres of prime cork forest. This tree is the primary source of cork for wine bottle stoppers and other uses, such as cork flooring.
When it comes to wine, the natural cork is the only truly sustainable wine closure. Although Cork Oaks are harvested every 9 years for the life of the tree, Cork Oaks are not cut down to harvest the bark. Portugal accounts for 70% of world cork production.
But it wasn’t until the 18th century, when it became the preferred stopper of choice. You see, the old method of sealing wines in 18th century France was to take wooden pegs and wrap them with hemp soaked in olive oil to create the seal.
The change to cork came about because Dom Pérignon who developed the process for Champagne production needed to find a better way to prevent those gassy Champagne bubbles from popping the hemp-wrapped peg stoppers out.
With the older stoppers, the wine lost its sparkle and the Champagne became flat.
To find a way to keep the sparkle and the freshness, Pérignon started a series of experiments—whereupon he discovered cork fit beautifully. Cork worked so well, the entire wine industry ended up adopting it up as the standard for sealing wines.
So what makes cork so special?
Cork Oaks absorb carbon dioxide as part of their natural growth. The CO2 retention capabilities of Portugal’s cork forests are over 4.8 million tons annually with recycling adding to this life cycle. The average natural cork retains nearly 9 grams of CO2 throughout its useful life.
Cork is resilient and performs extremely well under pressure. It can compress to half its size, without bulging out the other side or increasing in length. The inside of a piece of cork looks just like a honeycomb. In fact, the cork honeycomb cells are extremely stretchy and filled with with about 90 percent gas, which makes it light and buoyant. This unique construction also allows the cork material to to be squeezed tight without collapsing under pressure. When the gas in the cells becomes compressed, it loses volume but it is always “pushing back” trying to regain it’s former volume which allows it to seal Cabernet and Champagne with ease.
Another plus, according to the United Nations’ Food and Agricultural Organization is that cork can stay submerged in liquid for centuries without rotting. This is due to a coating made of a complex mixture of fatty acids and heavy organic alcohols called suberin http://dictionary.reference.com/browse/suberin inside the cell walls of the cork. Suberin, plus tannin and a scarcity of albumenoids, help to make it decay and moisture resistant — making what is often called the best seal in existence.
Cork also cellars well as it allows for a small bit of aeration over time. All wines contain a small amount of a preserving/antibacterial agent, sulfur dioxide, without oxygen, that sulfur disintegrates and creates a smell like a struck match. Cork adds air naturally by releasing some of its stored gas, 3-4 milligrams. Cork’s gas release is internal, so there is no odor other than the smell of the wine. According to Amorim Cork America, the leading producer of cork, the incidence of TCA taint in cork shipments has dropped below 1.0ppt.
This means that when it is time to pop the top, both wine and cork come out unscathed—the wine appropriately aged and the cork looking almost like it always did.
It may be compressed by machines, jabbed by wine keys, and assaulted by liquids, only to bounce back to its original form—even after years of abuse, the cork doesn’t lose any integrity in its cell structure, maintaining its form so your Cabernet can, too.
If you enjoyed this article and would like to subscribe to receive notification of future Wine Examiner articles, simply add your email address to the subscribe button at the top of the page. Comments welcome.
Comments