Napa Valley Wine Radio

Question from Don: Does the type, brand, manufacturer, etc. of a cork used to seal a wine bottle have an impact on the wine in that bottle? Thank you.

Reply: Hi! Thanks for writing! What an interesting question.

I’ll assume that you’re asking about natural cork and say the answer is “yes.” The job of the cork is to protect the wine from air without imparting any flavor of its own. The cork can have a positive impact on the wine, when it does its job well, by allowing it to age, and a very definitely negative effect when it fails and the wine spoils. If the wine is intended for very long storage, the winemaker will likely select a relatively long, dense, high-quality cork. For short-term aging, the quality should still be high, but extreme length isn’t really necessary.

As with wine, there are numerous factors that contribute to overall quality, starting with the agriculture. Portugal is the biggest supplier of the world’s cork, but there are other choices such as Spain and Sardinia. Where the tree grows and how it’s nurtured until it’s old enough to produce wine cork, around 40 years of age, is key. Attention to detail at harvest and when sorting is also important. And then, there’s processing and quality control along the way.

It appears that, at least in Portugal, most of the forests are family-owned and that the cork suppliers contract with the families. In the case of our supplier, Cork Supply USA, the cork buyer works with the families throughout the year and, in a recent demonstration, we saw that he hovers over the men who harvest the bark while the work is done. As you might guess, some companies will show greater attention to detail and be more involved than others. What about the company that lets growers be growers and just collects the bark?

And then there’s this whole issue of cork taint. As you’re probably aware, the industry has been struggling with it for many years. By now, it seems that cork taint (TCA) is on the run, but each supplier has slightly different methods of decreasing or eliminating the taint. In this article one supplier kind of took a pot-shot at another supplier’s approach.

Our supplier has a greatly-improved ability to detect TCA in whole bales of cork, thanks to working with a local wine lab that uses “solid-phase microextraction”. And they’ve developed a machine that purges TCA down to the level of 1 part per trillion (human threshold is 4 to 8 parts per trillion for most of us). So, you can see why we choose to work with them.

All of this is good news, because the overall incidence of cork taint is way down, now, and hopefully completely on its way out. And with cork taint out of the picture, natural cork has otherwise been an excellent seal for many centuries. Some are denser than others, some have more or fewer flaws, but most suppliers give the buyer the option to choose. My guess is that most of these suppliers are doing a good job or they’d be out of business. But, just as with wine, some are probably doing a little better job than others, and it’s our job as wine producers to track down the best.

There’s a little more detail on TCA detection and extraction from this previous
post, and if you’re in the mood to immerse yourself in the world of cork, you’ll enjoy this 4-part interview with our supplier. I hope this is helpful to you! Cheers! Nancy