I’m supposed to be writing about Burgundy, so why write about cork? I guess it’s due to a gradual build-up of pressure and this is my release. I had anyway done a little research and learned a few facts along the way, so I thought I’d share them with you. The spark to action came recently when I opened a bottle of Faiveley’s 1999 Chambertin Clos de Bèze, exactly the type of wine that someone might cellar for 15 years to open on a special day; almost the instant the cork was popped, the air became heavy with the smell of cork taint.

Now I know my local retailer pretty well (no surprise) and so was easily able to get a refund – and this despite the fact that the bottle had already been in my cellar nearly two years. Unfortunately a replacement was not possible as their stock was long since sold. But what if the bottle had been in my cellar for 6, 7 or 12 years? – where does the responsibility of the retailer stop and the responsibilty of the producer take over? There are some retailers who have a no returns policy – explained through low prices or whatever – for me, that means however good their selection or their prices, I can’t afford to use them – ‘sorry’ but I’d rather pay a little more – insurance if you like! Of course getting the cash back doesn’t compensate for not having the wine – though I do have another bottle in the cellar – somewhere (took a while but I found it!).

The truth is that I went through a bad phase of tainted wines in 2003, and although most of the wines were not of Burgundian origin, plenty, including the example above were. I did a quick calculation – easy when you’re sad enough to have notes on most of the wines – and found a total ‘taint-rate’ of 6% in 2003, just under half of that (2.5%) from wines from Burgundy. Thing is, Burgundy is my main area of ‘investment’ – the value of the bottles for that 2.5% far exceeded the value of the 9% (yes 9% – I drink mostly Burgundy!) tainted other bottles. I don’t remember the problem being so bad in 2001 or 2002 – maybe I’m becoming more sensitive.

Cork facts

With 800,000 tonnes per year of cork harvest, Portugal accounts for just over 50% of cork produced – the majority of the remainder coming from Spain and North Africa. This 800,000 tonnes equates to an income of 900 million Euros for the (roughly) 700 Portuguese companies involved, 3.5% of Portugal’s GDP and 80% of the income derived from Portuguese forests.

The time that you must wait before you can harvest cork is directly related to height above sea level that the cork oak grows – the higher the altitude the slower the growth (slower usually provides the highest quality though), so the longer the wait. On average the first bark harvesting is done at 20-22 years old, and then every 9 years. It’s only the third harvest that achieves the required quality, so the tree is at least 38 years old before it’s really producing, but can stay in continuous production for 200 years or more. Trees planted today are for the benefit of the producer’s grandchildren! The bark itself is actually part of the tree’s survival mechanism, hot Southern forests can be decimated by fire – unfortunately more and more common – but whilst cash crops like eucalyptus are completely destroyed all the cork oak requires is a few months of recovery; all the life-saving buds are saved by the insulating cork.

Applications for cork are as diverse as insulation for the Arianne space rocket, flooring and building materials. Even in death the cork oaks are fully used – the cork bark itself ends up as building materials, whereas the wood goes into kilns to make charcoal. Cork is also easily recycled so seems the perfect ‘natural’ product.
It is the cell-structure of cork that gives it the unusual characteristic of being elasticly compressible, without at the same time increasing in length – this is what provides the seal in the neck of the bottle. Provided the cork is not allowed to dry out, this seal should be good for 20-30 years. As an aside it was Sir Robert Hooke (found elsewhere in this issue) who was in 1665 the first person to see and name cells. He examined cork bark with his primitive microscope and saw the little cubicles which he called cells!

The process

From start to finish the production process is very labour intensive: The ‘raw’ bark is left outdoors for a few months to stabilise in the wind sun & rain. Next, it is cooked in boiling water for an hour to kill insects and remove water soluble impurities (eg phenolic acids) that could taint the wine – though this can increase the vanillin component. This boiling helps makes the cork ‘planks’ a little flatter and easier to sort. The sorting is done by hand after a few days of drying. Around 30% of all cork ends up as wine ‘stoppers’, manually punched out of the planks. The remaining majority is often ground and compounded into sheet material for the other applications. From the cork chopping/boring machine the corks go through a disinfection process and are then hand sorted. Whilst the highest quality corks are not so cheap – perhaps as much as 1 euro each – they would be considerably more expensive were it not for the low average wages in the region.

As the cork taint problem gains higher profile, it is the disinfection process that has come under most scrutiny. After stamping out the corks, they are washed in a solution of calcium hypochlorite to bleach and sterilise the corks, and then rewashed with oxalic acid to remove the bleach. The oxalic acid also has the role of removing any iron particles which could come from previous stamping/cutting processes and would form black deposits with the tannins in the wine. Chlorine remaining in the cork (from the bleaching) favours the production of the main compound to taint wine.

The stoppers are stored for 2-3 weeks until the moisture content is around 10-12%: Above this level, mold is possible, as is the potential for ‘squeezing out’ remaining liquid from the cork into the wine when inserted under pressure into the neck of the bottle. They are stored in plastic bags for transport in containers, avoiding further exposure to contaminants.

The problem

Shorthand it’s TCA – or 2,4,6-trichloroanisole to its confidants – recently augmented by its sibling TBA or tribromoanisole. TBA is a constituent of flame retardants (sometimes referred to as intumescents) and their derivatives, whether used on buildings or on your home’s upholstery. Given the fact that the ‘discovery’ of TBA as a potential source of taint is relatively recent, I will take the opinion that it is a rare phenomenon and ignore it for the purposes of this discussion.
Time to focus on TCA…

TCA it seems, is always with us; at the limits of detection for modern analytical equipment, all corks, whether they taint the wine or not, contain tiny amounts of TCA – it seems that we are troubled by our own attempts to have clean stoppers as the problem is derived from our own ‘cleaning process’.

Whilst everyone’s skill is at a different level, we can typically detect TCA at only a few parts per billion. The effect on you favourite beverage can range from the blindingly obvious example of the Clos de Bèze to wines that simply disappoint in their dull presentation – these are wines where the TCA level is below your own detection level, but high enough to disrupt your perception of flavour and aroma components. Often described as an aroma of wet cardboard, I prefer a descriptor more like newly sawn wood – or like opening crates of Bordeaux wines. Personally speaking, if close to my own detection limit, I’m more likely to note the presence of taint on the mid-palate and finish than the nose – but we’re all different.

Official – whatever that means – figures indicate rates of corked wines between 2 and 7%, in perspective that means possibly one corked bottle in every case that you buy – just imagine if your 1999 Romanée-Conti is the one…

Discussion

So it’s a nice story of environmentally friendly production and disposal and everyone should be happy then(?) If it wasn’t for the taint issue I would say yes, though I should just mention that TCA is not the sole cause of cork related problems, the much rarer, completely oxidised bottle is testament to a seal that is not always a seal – but TCA is the most prevalent issue, and certainly has the highest profile.

As the ‘curse of TCA’ dominates more editorials the involvement of ‘interest groups’ becomes insidious. Two obvious examples on opposite sides of the debate are the cork producers with a livelihood and a chunk of their country’s GDP to protect, and then there’s the producers of alternative closures selling snake-oil to the masses. The cork producers can muster environmental groups, concerned that the forest ecosystem could be concreted over if no-one buys cork stoppered wine. The snake-oil producers (sorry I meant alternative closure manufacturers – pardon me) have any number of wine producers willing to exploit a gap in the market and sell wine stoppered with synthetics or ROTEs (roll-on-tamper-evident – most famously Stelvin) without regard to whether the wine will (on average) be any better.

So what are we to make of the situation?

History and experience shows that cork is an excellent sealing mechanism – problem is we have no way of telling which ones will ruin our wine BEFORE we put them into the neck of a bottle.

The cork producers are looking at microwaving, gamma radiation and even supercritical fluids to overcome TCA and I wish them luck – I like the ritual of the corkscrew – but I don’t like TCA. Some people suggest they would rather drink coca-cola than remove a screw-cap from a wine-bottle… my question to them would be: what about the other people around the dinner table who will not be party to this (your) ritual?

Regarding synthetics I have to say that I’m sceptical. My scepticism comes from many years in the chemical industry and the sure knowledge that everything has some level of solubility – from complete solubility to only parts per billion. So what are those plasticisers and how much are in my wine – plus it takes as long to get the damn things off my corkscrew as to get them out of the bottle! Then there is that grey area between cork and synthetic where chopped up cork is mixed with an adhesive to produce the worst of all worlds – my anecdotal experience is that taint incidence increases by around 3x for thes abominations.

And the ROTE’s? Frankly, if they have 20+ years of data vs well stored, good corks then I’m in. I don’t see it yet, and presumably neither do the producers of the worlds great wines – they don’t just use cork because Portugal’s a nice place that supports Lynx – they do it because the jury is still out and, just maybe, very soon, supercritical fluids (or whatever) might fix the problem.

It’s a frustrating wait though, particularly on Chambertin Clos de Bèze days…

Just in case I’ve piqued your interest, Jamie Goode has the best independant web reference covering the dynamics of the ‘closure’ debate.