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Lise Ciolino
February 15, 2010 | Cork, Environment, Packaging | Lise Ciolino

The Great Cork Debate

Have you ever wondered why Montemaggiore wines are sealed with a cork instead of a screwcap, for example? Having just finished reading "To Cork or Not To Cork: Tradition, Romance, Science, and the Battle for the Wine Bottle", Lise figured this is a good time to contemplate wine bottle closures.

Corks started being used regularly as a stopper for wine bottles in the mid-1600s (replacing the oil-soaked rag). They are punched from the outer layer of bark of Quercus suber. With ~5.5 million acres of cork forests worldwide, about half of the production is from Portugal and a third from Spain. Once the trees are about 25 years old, the dead outer layer of the bark is stripped every 9–10 years, leaving the living inner bark layer. The oldest known cork oak which has planted in 1789, yields more than 100,000 corks each harvest. About 80% of all cork harvested is turned into wine closures, while the percentage of wine closures made from cork is about 75% (down from 90% twenty years ago).

Cork is an absolutely amazing material, and nearly perfect as a wine stopper. The cellular structure of cork enables it to be easily compressed upon insertion into a bottle and then to expand quickly to form a tight seal (98% expansion in 24 hours). Since the neck of glass bottles is notoriously variable and uneven, this and its water tightness are very important attributes. Nearly 90% of a cork's volume is made up of tiny, trapped air pockets which give it its buoyancy and compressibility.

Being a natural product, cork is not entirely perfect. Historically, its been the source of TCA (2,4,6-trichloroanisole), which can give a bottle of wine a musty, wet-cardboard aroma. TCA in corks was reponsible for the nomenclature of a "corked" wine. While TCA poses no health risk, even minute amounts can destroy wine quality. In recent years, cork producers have vastly improved their quality: developing methods to remove naturally-occurring TCA and prevent its formation. In fact, more recently wineries themselves have been the source of much TCA in wine. TCA is formed by the combination of wood, water, and chlorine (a common winery disinfectant)—it can become airborne and contaminate winery equipment. (Note: this is why Montemaggiore's winery never uses chlorine, and was built without any wood).

Due to TCA (as opposed to cork scarcity), several alternatives to natural corks have been developed including plastic corks, agglomerated corks, glass stoppers, and screwcaps. Each has its advantages and disadvantages. For example, screwcaps are popular for early-drinking wines, especially whites. Screwcaps allow much less oxygen to come in contact with the wine, thus making the wine taste fresher and younger—but that can also lead to reduced, rotten egg-like odors. Lise believes that red wines, especially those which are cellar-worthy, need oxygen in order to reach their potential with layers of softness, richness and complexity.

Given the pros and cons, natural cork is Montemaggiore's closure of choice and we have had good experience with it.

  • We believe cork is the best closure for the long-term aging of high-quality red wines. Lise buys dense, high quality corks, and performs extensive sensory trials to choose specific bales of cork.
  • Cork is natural and unprocessed in keeping with our winemaking and vineyard management philosophies. It's also completely recyclable and reusable.
  • We prefer to support the environment of cork forests, over aluminum mines and smelters for example.

Having said that, Lise reserves the right to change her mind in the future as alternative closures are improved and new research comes to light! And if you ever feel that a bottle of Montemaggiore wine is tainted by TCA, please let us know since we stand behind our product 100%.

Further comments by Author

7/17/14 A recent study compared "good cork" with "bad cork" finding that with climate change, cork oaks may be producing more bad cork. Good cork has high levels of a heat-shock protein produced in response to ultraviolet light, high temperatures and drought. Bad cork produces more phenolic (flavor) compounds and has much thinner bark. See article in ScienceNews.


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