Cork v3.0 – Cork Fights Back

Cork oaks with their trunks stripped – photo courtesy of Diam.

The cork or screw cap debate is getting interesting again – click here for an article that I wrote about it quite a few years ago. For many years I, along with many in the British wine trade, have long championed the use of screw cap over cork.

My main reason for doing so is that for a long time we had far too high a proportion of bottles that were corked. This happens when a cork is infected by a compound called trichloroanisole, TCA for short, and that gets passed on to the wine in the bottle, killing the fruit in the wine and making it smell and taste musty like mouldy cardboard.

A compelling second reason to favour screw caps is that with corks there is a significant amount of bottle variation as some give a better seal than others, so little bit of oxidation can occur making some bottles seem less vibrant and more muted than others.

Screwcaps do not get rid of all of this, it is possible to get TCA into a wine by another route, so I have had 4 ‘corked’ bottles sealed with screw caps. That is 4 in over 20 years though. By comparison my record for corked wine that was sealed with corks was 6 bottles from a single case on a single day!

I also like the glass closures, they look very classy and I think if I made wine that is what I would choose. The rather more funky  Zork closure is rather good too, especially for sparkling wine.  It makes a noise like a cork popping and you can reseal it.

However, many people are more traditional than me and like to cling to things because they are used to them or sometimes because they think they are best and so cork is still used to seal the majority of wine bottles.

In the 10 years from 2006 to 2106 the use of cork has dropped from 78% of closures to 61%, so it is still the dominant material. In that time screw caps have grown from just 5% to 26%. If those figures seem low to you, outside of the UK, Australia, New Zealand and Switzerland, cork is considered superior and screwcaps are widely viewed as suitable only for the cheapest wines.

The tops of various types of cork.

Well cork seems to be fighting back and the charge is lead by a new form of cork that manages to get round the traditional problems that cork has.

Natural cork.

Most of you will be able to picture a traditional cork, that is a cylinder of cork stamped out a single piece of cork oak bark. Being a single piece if it is contaminated by TCA, this will infect the wine.

Agglomerate cork.

Agglomerate cork was an attempt to get around that by making the cork out of lots of tiny pieces of cork glued together. However these are usually considered less suitable for ageing wine as there is almost no oxygen ingress, or trickle of oxygen through the cork, to age the wine. In addition they are less pliable than natural cork, so again less suitable for long term ageing.

Synthetic cork.

Synthetic corks have certainly proved to be effective for early drinking wines. The risk of TCA infection is almost completely removed, unless TCA gets into the wine via wood or filter pads or by another route – this can also happen with screw cap wines, but it is rare. However many of them can harden over a relatively short time, making them less effective and allowing air into the wine. Added to which they are really difficult to get off the corkscrew once you have removed them from the bottle. In my opinion these are really only suitable for early drinking wines, but a screw cap would be a better seal and preserve the fresh character of the wine and the fruit much better.

Recently I was invited to France to tour a cork factory that belongs to a company that is changing everything – that company is Diam.

A Diam 3 cork.

Basically Diam manufacture a type of agglomerate cork, but a very high tech and high quality one. I cannot pretend to understand the science, but basically they harvest high quality cork, season it outside for up to 12 months, just as natural cork would be. They then wash it and crush it into granules which are then filtered to remove foreign bodies and the woody parts. This leaves them with pure suberin, which unlike lesser cork is inert. This substance undergoes a similar process to the one that removes caffeine from coffee, which removes all impurities from the cork granules, they actually store the TCA that they remove as it can be used in the manufacture of some skin creams – so the next time auntie smells of cork taint, perhaps she hasn’t been drinking! The gaps between the cork granules are filled with microspheres which increases the elasticity of the finished cork. They are then bound together with a food grade binding agent before being moulded, machined and finished to the correct size and finish.

They tell me that with their process there is no risk of TCA, the cork is pliable enough to ensure there is minimal risk of premature oxidation – which makes Diam corks particularly popular in Burgundy – and stops bottle variation as they perform consistently.

If you look at the Diam cork above, you will see in the bottom right it says Diam 3, they actually make Diam 2, Diam 3, Diam 5, Diam 10 and Diam 30 for still wines, the number tells you how long they guarantee the cork for. They also make sparkling wine corks and spirit stopper corks.

An unused Diam 5.

It was a fascinating visit. The factory floor was almost entirely unmanned, with robotic machines doing all the work. The whole place had a rather wonderful toasty, malty, toffee, caramel sort of smell which is what the corks smell of when still warm.

Our little group on the factory floor and yes that is Charles Metcalfe in the centre. I reached the conclusion that the protective clothing was a French joke as none of the management wore it!

Diam corks are tested for their elasticity as they want them to be as pliable as possible. This elastic property ensures that they give a perfect seal and apparently do not need to be kept damp – so if you know it has a Diam cork you do not need to lie it down, or so Diam say.

Diam Origine.

Diam have been around since 2005 and their share of the market keeps rising, their share of the cork market has risen from a very healthy 4% in 2006 to 10% 10 years later. And by the way that 10% represents 1.3 billion corks a year!

Now they have launched an organic version called Diam Origine. Initially this will just be in a Diam 10 and a Diam 30 version, but more will follow. The organic corks uses beeswax emulsion and a binding agent made from plants and I expect that we will begin to see them used on more and more organic and biodynamic wines.

The Pic du Canigou from Diam’s factory near Collioure in the Roussillon region of France.

It was a very different visit from my normal wine trips, but it was very interesting and informative and the weather was gorgeous, the only lovely weather I have had this year so far. I was very impressed by what I saw and heard and feel much more confident about cork now than I have for a long time, as long as it is Diam.

It’s just a pity that you cannot tell whether the wine is sealed with a Diam cork before you buy it. Perhaps they ought to find a way of letting us know before we part with our money?