Put a _____ in It!
Just as there is a variety of wine styles on the market, there exists a variety of closures in which to seal those wines. If you’ve ever opened a bottle of wine a noticed it smells a lot like a damp newspaper or a wet dog, you’ve experienced one of biggest, most disappointing problems facing wine closures today, and that is what’s referred to as “cork taint," i.e. "corked" wine. Here we examine issues such as cork taint, as well as some other common problems associated with various closures, and how the closure industry is evolving to address these issues.
Natural cork is harvested from the bark of the oak tree, Quercus suber, and is considered to be one of the “greenest” and more sustainable types of closures. Each Quercus suber tree lives to be about 200 years old, and in that time one can harvest cork from the same tree every nine years without causing significant harm to the tree. Finally, these forests are known to be home to several endangered species, and represent the livelihood of many communities in Portugal, Spain, and the surrounding areas.
There is one major problem with natural cork that has many interested in alternative closures, and that is the risk of 2,4,6-trichloroanisole (TCA) contamination. This compound is responsible for what is commonly referred to as “cork taint”, which is represented by strong off-flavors such as moldy newspaper or wet dog, and is believed to be caused by microorganism growth metabolites or chemicals used during production. The rate of TCA contamination in wine has been shown in studies to be anywhere between 1% and 7%.
Technical corks, like natural corks, are made from the bark of Quercus suber, and are composed of little pieces that have undergone a battery of extra washing, sterilization, and treatment procedures. Many of these procedures have been successful in lowering TCA contamination rates, with some reducing TCA contamination in wine by 80%.
Despite this decrease in TCA contamination with technical corks, the risk of cork taint is not eliminated. Thus, there has been an increase in the production of synthetic corks, utilizing materials other than natural cork, such as low density polyethylene and similar plastic compounds. While the use of synthetic cork eliminates TCA contamination, the problem now becomes the rate of oxygen ingress into the wine. Some synthetic corks have been shown to increase the oxidation rates in wine and reduce shelf life. Some manufactures, like Nomacorc (Zebulon, NC), have made significant improvements in the oxygen management of their closures, and have improved their production methods to create closures that minimizes the risk of oxidation of wine, though this appears to be extremely variable from company to company.
While screw caps completely eliminate the risk of TCA in wine, the problem of reduction becomes more prominent. Oxygen is unable to transfer through the screw cap, thus allowing sulfur compounds to accumulate in the wine and create reductive off-aromas like flint, cabbage, and mercaptan. The rate of reduction in wines closed with screw caps appears to be very similar to the rate of TCA contamination in wines closed with natural cork.
The Future of Wine Closures
At VinExpo recently, the twist-off cork closure, Helix, was introduced. The general idea behind the Helix is that it’s easy to remove from the bottle without a corkscrew, though it’s still composed of traditional cork material that many associate with higher quality wines. According to company research, the Helix twist-off cork does not appear to alter the aroma or flavors of the wine, though this research has not yet been released to the general public. It will be at least two years before this new closure finds its way into the market, and hopefully by then we’ll have access to research on TCA contamination rates and other potential problems (if there are any)with this new type of closure.
There are many closures utilizing other materials and production methods on the market today, though comparative studies between newer closures and more traditional closures are few and far between. In addition to the problems of TCA contamination and reduction, addressing issues related to environmental sustainability is something that should be considered in the creation of new types of wine closures, with the final product not only resulting in a well-protected wine, but also a closure that is “environmentally friendly” and sustainable.