The great closure debate

Put a cork in it (or not)
The great closure debate grinds on.

There's less common ground in Closureland than in Gaza City. The anti-cork contingent produces ever-growing mountains of evidence about the shortcomings of the bark of the cork oak. Traditionalists squawk about the risk to the habitat of a number of non-wine consuming mammals and birds.

 

It's difficult for either side to yield their entrenched positions. The corkophiles would rather see ersatz cork than screwcaps. The Stelvin brigade cries "taint!" even before the stopper has been drawn from a bottle.

Since screwcaps themselves cannot taint wine, the Defenders of Cork have happily blamed the closure for the failure of producers to manage the higher risk of reduction when Stelvin is used. Screwcaps are pretty much as airtight as a seal can get.

This means that the reductive pong which can develop in an anaerobic environment is likely to occur if the wine hasn't been properly prepared for bottling. Condemning the closure for the fault of the technician is a little like blaming Mercedes because you crashed into the back of the car in front of you while talking on your cellphone.

Still, while the battle lines haven't moved, the ground underfoot has changed a great deal. Firstly, extensive research in Australia has shown that random bottle oxidation - possibly an even more important long-term problem than taint - is vastly less predictable with cork and disastrous with the plastic fakes.

Several of the latter have been known to conk suddenly (but only after a year or two, so they are still quite useful for wines destined for early drinking). More seriously, the variance in the gas permeability of real cork can range by a factor of 1 000! Corks which look and smell the same may either work perfectly well, or let you down really badly. That's a little like not knowing to what extent - if at all - the parachute will open every time you jump out of an aeroplane.

On the positive side of things (insofar as the corkophiles are concerned), Diam agglomerates seem to be successful. If you do want the appearance of cork, together with a reliable and taint-free seal, this is probably your best bet. More importantly, now that the cork suppliers are feeling the cold chill of potential redundancy, they have finally cleaned up their act considerably. The latest batches of cork-sealed young wines are showing significantly reduced levels of taint.

Back then to the question of permeability. The case for permitting the limited ingress of oxygen is that, without it, wine development would simply be arrested. Michael Brajkovich of Kumeu River in New Zealand disposed of this several years ago. "Studies have shown remarkable variability in the gas permeability of corks...If oxygen was so important in bottle age, we would expect to see even more variability in aged wines than we currently do. My suspicion is that the best ageing conditions occur when gas exchange is minimised... These favourable conditions are perfectly uniform with screwcaps."

Now we have a study which shows that random bottle oxidation also occurs as a result of the air trapped in the headspace of the bottle. The research, conducted at Geisenheim in Germany, measured what is called the Total Oxygen Package and showed that there could be as much as a 12-fold variance.

So where does that leave us? With cleaner, taint-free corks, but still with no fix for the varying levels of permeability. With Diam addressing some of these concerns, but untested over an extensive period. With ever-improving screwcaps advancing too fast for there to be any valid long-term research. And with the discovery that human error at the bottling line may be more significant than anyone realised.