The Lofty Role the Lowly Natural Cork Plays in Your Wine

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Nick Antonaccio
Nick Antonaccio

The otherwise mundane natural cork stopper has gained greater respect over the last year than at any time this century.

Natural cork fell out of favor with the advancement of alternative bottle stoppers. Synthetic, glass, agglomerated corks (particles of natural cork glued together) and metal screwcaps gained popularity.

Today, the consensus favors natural cork and screwcaps, although the growth of screwcapped bottles seems to be waning. Consumer opinion rides high for the screwcap, not only for its convenience but also for the soiled reputation of natural cork that had significant levels of cork taint for a number of years.

However, many winemakers favored natural cork for its ability to interact with, enhance and preserve wine as a living, breathing organism.

As alternative stoppers grew in popularity, natural cork producers responded to their threat. The Portuguese cork industry, which dominates the market, undertook to remove the causes of cork taint and was successful in the near eradication of this perennial problem.

In the process of researching, and improving, the quality of cork, Portuguese scientists discovered its previously unknown qualities. Cork not only performs as a stopper; it affects the quality of the contents of the bottle it secures. And it depends how it is deployed after bottling.

Perhaps the cork is much more than a functional closure. Perhaps it has inherent qualities that affect the quality and characteristics of the bottled wine. And perhaps lying horizontally may not be its best use.

Let’s explore these two concepts of functionality and preservation.

Functionality: The Drinks Business, a trade publication, reported on a research paper in the Journal of Agricultural and Food Chemistry concerning the impact of certain compounds in natural cork on the aging and quality of wine. The Drinks Business interviewed Dr. Miguel Cabral, director of research and development for Amorim Group, the largest producer of natural corks in the world.

Cabral: “Amorim was attempting to put the science behind the belief that wine matures ‘differently and better under cork.’ When we put wine in a barrel there is an extraction of phenolic compounds from a barrel into the wine, and it’s the same when we put wine in a bottled seal with a cork.”

These compounds include tannins, phenols and polyphenols. Cabral has identified 40 different extractible compounds in a natural cork that may be beneficial to the aging of wine.

Preservation: The common belief is that storing a bottle on its side will keep the cork moist and swollen, thus preventing it from becoming dry, shrinking and permitting external oxygen from permeating the contents.

According to Cabral, storing a wine bottle on its side makes no difference to the moistness of the cork. If anything, it may hasten its deterioration. This startling assertion is based on Amorim’s research results. “(H)umidity in the headspace of the bottle, at almost 100%, was high enough for phenolics to migrate from the cork stopper into the wine when the bottle was stored upright,” Cabral stated.

Further, “when you put a cork stopper in a bottle, the cork is squeezed and the air in it will compress as much as it can and then try to escape, and some of it goes up and some goes down, and so the oxygen comes from the interior of the cork, and comes in [to the bottle] up to 6-8 months.” He added, “the network inside a cork is complicated, with millions of cells, so the air escapes slowly and then less and less.”

Startling to say the least. The symbiotic relationship of a cork and the bottle contents with which it interacts is highly complex and seemingly contradictory. Is it likely that modern science trumps centuries-old trial and error?

There are additional factors affecting the ageability and quality of wines. In future columns I’ll delve into two of these: humidity levels and temperature of the bottle’s storage environment, each key to the ability of cork to impart its unique characteristics.

Nick Antonaccio is a 40-year Pleasantville resident. For over 25 years he has conducted wine tastings and lectures. Nick is a member of the Wine Media Guild of wine writers. He also offers personalized wine tastings and wine travel services. Nick’s credo: continuous experimenting results in instinctive behavior. You can reach him at or on Twitter @sharingwine.


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