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  • Jancis Robinson
Written by
  • Jancis Robinson
19 Aug 2017

21 August 2017 See an interesting addition at the bottom of this article. See also More on Diam published today.

19 August 2017 A shorter version of this article is published by the Financial Times. 

In the first decade of this century, many were predicting the demise of the cork industry, centred on Portugal, so popular were alternative wine bottle stoppers such as screwcaps and synthetic corks becoming.

The problem was the shockingly high incidence of TCA, the abbreviated name of the compound responsible for the most common sort of cork taint, in natural corks. Until recently all corks were made by punching little cylinders out of strips of cork oak bark, and trying, not always successfully, to keep the process as hygienic as possible. Far too many wines have ended up infected with TCA, either massively, in which case the wine smells undrinkably mouldy, or (worse for wine producers) mildly – in which case drinkers are likely to think it's the fault of the wine rather than the cork.

Australian and New Zealand wine producers became so frustrated with the poor quality of corks they were sent back in the 1990s that most of them have switched wholesale to screwcaps, which do the job of keeping wine's enemy, oxygen, out extremely efficiently – initially too efficiently but now most producers have worked out their ideal OTR (oxygen transmission rate) and choose screwcaps they think will allow the right amount of oxygen through the lining of the screwcap to facilitate the wine's ageing process.

Screwcaps have become so popular for cheaper wines that they are now to be found on about a quarter of all the 18.5 billion bottles of wine that need a stopper each year.

Synthetic corks, the ones made of plastic or, from the market leader Nomacorc, a sugar-cane derivative, are about half as common as screwcaps and are used mainly for less expensive wines in countries such as the US and France, where screwcaps are not widely accepted.

Screwcaps are the cheapest stopper of all, which presumably adds to their popularity with wine bottlers, but I for one admire those producers of superior wine who would rather sacrifice scorn from the odd uneducated consumer in exchange for guaranteed freedom from TCA and 100% consistency in how the wines develop.

Inconsistency of wine evolution has been the other big problem with natural corks, each one of them varying slightly in how much oxygen is available in each bottle. I have had bottles of the same wine from the same case, such as the two halves pictured below, that have been unrecognisably different, one from the other.

Climens_88_halves_large-3.jpg

At one time it looked as though the cork industry was under threat, but thanks to the rapid growth of bottled wine in both the US and China, the dominant natural cork supplier Amorim of Portugal has seen six consecutive years of sales growth. They report they are now selling two billion more corks a year than they did when screwcaps and synthetic corks started to make a real impact.

One reason why quality-conscious wine producers now look more kindly on corks is that – at long last – guaranteed TCA-free options are available.

One of the two major new wine bottle stoppers currently fighting for business at the top end of the market is Diam, owned by a French company that also owns important coopers Seguin Moreau (and recently bought a more commercial natural cork producer in Portugal). The Diam technical cork was launched in 2005, and from a standing start now sells 1.25 billion stoppers a year, including the Mytik sparkling wine version.

Diam corks don't look that great. Visually they bear a similarity to the cheap agglo corks made up of lots of little cork particles glued together, but in production method and efficacy they are quite different. I will spare you the intricate detail that so inspires Diam's team of food technologists, but basically they buy cork from around the world and, at their plant just over the Spanish border from Portugal's cork country, treat it with supercritical carbon dioxide, the vital element that is somewhere between a gas and a liquid, to eliminate 100% of the volatile molecules that might alter flavour. (There are now other, rival products that guarantee elimination of up to 80% of possible TCA.)

The cork is reduced by 60% of its volume to tiny grains of suberin, the soft, doughy bit of cork bark, and this is then moulded into cylinders with FDA-approved blending agent and microspheres that prolong the life of the cork. The finishing and printing take place all over the world in their finishing centres such as the one they operate jointly with California wine giant Gallo.

The process was initially used in the food and cosmetic industries – the parfumiers of Grasse are able to preserve delicate rose aromas because of it, for example – and the patent for the process as applied to cork is held jointly by Diam and, of all organisations, the French atomic energy authority.

At their plant in Céret near Perpignan (pictured above right; it dominates the town's landscape), I was shown the tank below, proudly shown off by Diam's European marketing director Pascal Popelier, full of extracted TCA, which, I was told but found hard to believe, is destined for the cosmetics industry, an anti-ageing cream this time.

TCA_tank_at_Diam-4.jpg

All Diam corks are marked Diam somewhere, so, only once you have pulled them, you can tell that your wine was neutrally sealed. I complained to Diam's head of R&D that Diam stoppers are so inelastic that they are pretty hard to reinsert into a bottle neck (though not as hard as the early synthetic corks). 'Exactly!' he beamed. 'This shows how good they are at their job.'

I'm noticing Diam more and more, and would love the producers who use them to advertise the fact – as of course would those who sell them. They guarantee both 100% removal of TCA and 100% consistency of wine evolution.

Within France, Burgundians have been keener Diam customers than the Bordelais, particularly for their white wines, presumably in the wake of their difficulties with  premature oxidation. The Diam team is especially proud of Louis Jadot's decision to stopper all their grand cru white burgundies with Diam, which comes in several different versions, according to OTR and guaranteed life of the cork – D1 to D30, guaranteed to last 30 years. (Burgundians choose minimum OTR.)

In practice, wine producers tend to trial Diam for their less expensive wines before moving on to use it for the top of the range, which from a consumer's point of view is a little frustrating. Mytik has become so popular with Prosecco producers that total Diam sales to Italy are likely to overtake those to France this year.

But Portuguese cork producers Amorim and MA Silva now offer natural corks they claim are TCA-free. Amorim launched theirs, ND Tech, at the end of 2015 and expect to sell 50 million of them this year. NDTech (the Diam team, most famous producers of 'technical corks', seemed flattered that Amorim chose to append 'tech' to the name of this premium product) is quite a different animal from Diam. It is the crème de la crème of their natural corks, subjected to such a rigorous selection process that the company can guarantee that any remaining TCA level will be well below the perception threshold. But the process takes so long that at present it can yield only three corks a minute.

Those already using NDTech, such as Ch La Conseillante in Pomerol, report that they are already enjoying wine evolution that is as consistent as it would be under screwcap.

THE PRICE OF A STOPPER
The following are very rough comparative prices per thousand wine bottle stoppers as charged to a small wine estate.

  • Synthetic corks €70-€250
  • Stelvin screwcap €100 (cheaper alternatives are available)
  • Diam 5 €170
  • Diam 10 €220
  • Top-quality untreated natural cork €300-€400
  • Vino-Lok glass stoppers €450-€1,100
  • NDTech €500 (a similar product is available from MA Silva)

Ken Lamb, a London-based wine lover with a strong business background, sent this particularly pertinent comment:

It has been fascinating to be vice chairman of Vinventions, the holding company for Nomacorc, Ohlinger, Vino-Lok, etc. I visited the R&D team in the south of France a couple of years ago, which is an amazing experience for a wine geek.

Vinventions was established because management assessed the fragmented closure market and the varying needs of winemakers and consumers, and concluded that no single kind of closure is ideal for all wines/circumstances. So, it offers closures made from a variety of polymers, one-piece natural cork, screwcaps and, very soon, SUBR, a combination of TCA-free cork particles (as in Diam) and a natural product-based (corn) neutral polymer.

Diam has its line of micro-agglos also made from similar cork particles and a variety of binders, including Origine using beeswax and other materials as binders.

In my view, the next few years will be an interesting battle of sales and marketing continuing to argue about: (1) OTR issues (particularly consistency in one-piece natural cork and screw cap, when OTR is considered desirable); (2) whether micro-agglos leach anything into wine and whether partly based or full-based polymer closures impact the smell/taste of wine; and (3) as ever, cost. I expect that the better driven closures and screw caps will all offer equivalent ease of use, although I'm not sure whether the problem you had with reinsertion will be solved ... too soon to tell. At the finer wine end, the ability to use Coravin effectively will have a role for some consumers and, increasingly, restaurants.

Aesthetics across all closures will also be important ... printing on screw caps ... whether polymer-based and micro-agglos mimic the look of one-piece natural cork or not, etc.

As TCA has become less of an issue with better closures, the issues debated and that are relevant to producers and consumers have changed and also continue to differ dramatically by market. It's a good time to be a wine consumer, as the quality of closures made by the better closure producers has evolved to a very fine level of quality (still, of course, with some issues) in the last decade.