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What About Plastic Corks and Screw caps?
This is a subject that has raised a lot of questions because things have changed rather rapidly. Lately, when you buy wine you’ve probably noticed that, more and more often, the standard natural cork has been replaced by other closures like plastic corks or screw-caps.
Why is this happening? The two main reasons are cost and frustration due to imperfections in the cork. Here’s a little background:
The first duty of any closure is to seal the bottle and protect the wine from oxygen. In that regard, cork has proven to be an excellent closure over a number of centuries. It swells when it comes into contact with moisture and creates a tight seal. The downside is that cork is the bark of the cork oak tree, and we can’t exercise absolute quality control over tree bark! Click here for “Corks: from the tree to the bottle”. If the cork fails to perform properly and doesn’t swell into the neck of the bottle, the wine is exposed to too much air and it spoils. Fortunately, spoiled wine isn’t harmful, but it can be offensive. When the wine becomes oxidized, initially it may lose its freshness and fruitiness. As the spoilage progresses the wine browns and develops off aromas such as fingernail polish or vinegar.
The most common problem associated with cork is that sometimes microscopic fungi, in the presence of moisture, convert naturally occurring chlorophenols into chloroanisole. The compound that gets into the wine is called 2,4,6 trichloroanisole, or as most prefer to call it, TCA. It can make the wine smell “corky” like an old, dank basement or moldy newspapers. Other chloroanisole contaminants have been identified, too, that similarly detract from the wine. The good news is, again, that it can’t hurt you. The bad news is that it stinks!
Corks aren’t the only source of TCA in wine. It can come from contaminated barrels, air-born molds or molds in containers, especially wooden boxes. TCA can also be found in fresh produce that has traveled in wooden boxes and in other food products due to contamination during processing. For wine, the cork is still the most likely culprit.
While the human threshold for detecting TCA is measured in parts per trillion, some of us are more sensitive than others. In very low concentrations, TCA may simply deaden the fruity aromas in the wine without it being obviously due to cork taint. As the level increases, it becomes more identifiable and offensive.
The exact incidence of cork taint is hotly debated. Estimates range from one to 8 percent. This is true regardless of the region of origin or quality of the wine. Quality control can reduce, but not eliminate the incidence of cork taint. However, there’s some very encouraging work being done in this area. For more on this click here for “Corks, from the tree to the bottle.”
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