Wine and Cork - Why Do They Need Each Other So Bad

Cork plays a critical role in the wine business. It has historically been the most used closure and nowadays it closes around 70% of all the wine bottles in the world. However, in the last decades both screw caps (made out of aluminum, with around 19% market share) and synthetic corks (made out of plastic, with around 11% market share) became more and more popular. Why? I would point two main reasons:

• screw cap is easier to use than cork, avoiding the need of a cork screw to pull the cork out of the bottle;
• both screw cap and synthetic cork are trichloroanisole (TCA) free, while few decades ago cork had problems of TCA contamination (which above a certain level may spoil the wine)

Despite that, cork is still the most used closure. Why are wine producers so keen in using cork? I’ve recently visited Corticeira Amorim factory and tried to understand a bit more about the motivation for using cork. I’ve also read few article about which closures to use for wine and found some stunning research (check bibliography at the bottom of this article). Putting the environmental question apart (cork comes directly from the bark of the cork tree grown naturally), there are two factors that help cork to be the closure that ensures the best quality for a bottle of wine:

• all the oxygen that passes to the wine comes from within the cells of the cork, and not from the outside; thus cork stoppers are effective barriers to the transmission of exogenous aerial volatile compounds, while synthetic closures allow contamination and oxidation from outside.
• given their relatively high oxygen permeability, synthetic closures promote the wine’s development towards oxidation faster than the other closures. In contrast, reductive off-flavours have been reported to happen more frequently in wines sealed under screw cap, which is argued to be related to their low oxygen permeability compared with other closures.

Regarding to Port Wine, back in 2008 I knew of one Port producer, Castelinho, using not only natural cork. They were using synthetic corks is some of their references. Currently, don’t know any. However, legislation does not allow the use of screw cap but only natural and synthetic corks  (the only exception is the very small size bottle which can be sealed with screw cap). Though I’m sold to natural cork for Port, I disagree with the prohibition of using other closures. Producers should use what they think is better for their wines and Ports. Through experiments of different closures, we could see and taste how different closures perform in a bottle of Port. And eventually we might come to the conclusion of what closure is the most indicated for Port. But through our own experiencing, not by law.

Oscar

Bibliography – If you want to know more about these three closures I suggest you to read:

• Impact of different closures on intrinsic sensory wine quality and consumer preferences
• The impact of closure type and storage conditions on the composition, colour and flavour properties of a Riesling and a wooded Chardonnay wine during five years’ storage;
• Sealing effectiviness;