The case for screwcaps

Following Drinks International's report in September on the progress being made by cork producers in their fight against faults, James Halliday points out TCA is not cork's greatest failing
27 August, 2008
Page 26 
Those who have visit ed Portugal over the past 15 or so years will know that, after a decade of denial, the country's cork producers have spent a small fortune on radically changing their procedures, from the moment the bark is stripped from the tree to the time the finished corks are despatched to wineries around the world.

The investment has resulted in a substantial decrease in the percentage of corks with trichloroanisole (TCA for short) taint, which manifest s as a musty, mouldy, bitter aroma and taste. It is worth noting that humans can detect the presence of TCA in minute concentrations - so minute that testing methods have only recently caught up with the human nose. It is no surprise that Charles Walter Berry, of Berry Brothers & Rudd, wrote in 1932 in A Miscellany of Wine : "The 'corked' bottle we all know, and none of us understand. Happy will be the man who can find out the cause and the remedy."

Before moving on, winemakers who sweat blood to put wine into bottle as perfect as they can achieve should not be inclined to accept the proposition that even 1 per cent of the bottles should be contaminated, let alone higher percentages.

This, certainly, was the view adopted by the Clare Valley makers of Riesling, who moved en masse to screwcaps in 2000, and New Zealand's makers of all wines shortly thereafter. (At the 2005 Auckland Wine Show, all 13 trophies for still table wines - white and red - went to wines with screwcaps.)

Fast-forward to October 2007 and the 1,200 wines I tasted for my annual Top 100 in the Weekend Australian newspaper. In the under-US$20 white section, 96.8 per cent had screwcaps; under-US$20 reds, 88.4 per cent ; over-US$20 whites, 87.3 per cent; and over-US$20 reds, 57.2 per cent. The last figure is largely due to a vintage lag effect; in another two years the percentage will be close to 80 per cent.

The obvious question is why - if TCA (and other associated taints) is being reduced - Australian and New Zealand winemakers are irrevocably headed in the opposite direction. The answer was given well over 100 years ago by Louis Pasteur, who declared oxygen was the public enemy of wine. In 1898 another French researcher wrote: "In bottles, so long as the cork is sound of the wine is near absolute. New absorptions of oxygen are impossible." In 1947 Professor Jean Ribereau-Gayon came to the same conclusion; in 2000 his son Professor Pascal Ribereau-Gayon was equally emphatic that: "Reactions that take place in bottled wine do not require oxygen." End of discussion on point one: wines, white or red, sealed with screwcaps will evolve and develop in bottle in a not dissimilar fashion to corks.

"So what?" the cork apologists respond. Cork can achieve all that a screwcap can. Yes, but only one in 10 or one in 100 cork finished bottles can do so - the problem is that no two corks are exactly the same, whereas all screwcaps are.

Research by the Australian Wine Research Institute between 1999 and 2004 showed that screwcaps allowed between 0.0002ml and 0.0008ml per day of oxygen, and corks 0.0001ml to 0.1227ml per day. In other words, screwcap has a range of four times in permeability, cork 1,200 times.

So that random (or, technically, sporadic) oxidation of wine, courtesy of the cork, is the reason the elders of the English wine trade used to say : "There is no great old wine, only great old bottles ." It is also the reason for the stampede of winemakers in Australia and New Zealand away from cork to screwcaps.

Finally, let me lay the bogey of reduction to rest. Reductive wine -wine which has had no exposure to oxygen in its elevage, and has developed sulphide-like characters - will show reduced characters whether under cork or screwcap. It is the winemaker who is responsible for reduction, not the closure.

Further reading: The Great Closure Debate - Choices & Consequences, in the second edition of Art & Science of Wine, Mitchell Beazley, London 2006, by Hugh Johnson and James Halliday.