Recently we posed the much-debated wine question, corks or screw caps? the reaction was mixed. The responses we received suggested that the important aspect of buying wine, was the juice itself. It didn’t really matter if it was closed by cork or screw cap as long as the quality was there and the value for money was there. Some preferred screw caps due to the reduced risk in receiving a faulty wine. However some still persisted that only bottles closed by cork would do.
However recent research has suggested that the quality of the cork used for wine closures has been in a gradual decline for the past two decades. Studies from the University of Lisbon suggest it could be down to the climate shift and extra exposure to UV rays. Trees are adapting to their environment to protect themselves against radiation and in affect this is adversely affecting their suitability for high-quality cork closures.
Cork originates from the Quercus Suber, a slow growing, evergreen oak tree that gorws predominantly in Southern Europe, in places such as Spain and Portugal. It takes 25 years for the first harvest to be ready, however you won’t find this suitable for cork closures. The second harvest will take place 9 years later, and then the third harvest 18 years after that, 52 years into the trees cycle. It’s only when you get to the third harvest that you’ll find cork suitable for wine closure.
To make a high quality cork, you need the bark on the cork trees to be at least 27 millimeters thick, but most trees now are producing bark that is between 3 and 10 millimeters thick. The researchers at the University of Lisbon compared the genes in 5 high quality cork trees, to 5 low quality cork trees to better understand why the shift was occurring.
They discovered that in the high quality trees, there were more heat shock proteins, which help ensure the tree grows normally, even in adverse conditions. However the low quality trees had huge amounts of phenolic compounds which are UV absorbing chemicals, again suggesting that trees are adapting to protect themselves from the environment.
Metal screw caps are becoming more and more popular and if we continue to see the decline in good quality cork, that trend is only going to accelerate.