Closures: Part 4 – Synthetic solution for grand cru Burgundy

Our penultimate installment on closures considers synthetics and their adoption to seal the world’s most valuble wines.

Laurent Ponsot has sealed everything he produces from the 2008 vintage with a synthetic cork called AS-Elite by Ardea Seal; Photo credit: Colin Hampden-White

Having considered the use of natural corks and screwcaps for sealing wine, we wanted to look at the third most common option available to winemakers: synthetic closures. And it might be a surprise to learn that a fervent champion for these comes from Burgundy’s Côte d’Or; Laurent Ponsot from Domaine Ponsot in Morey-Saint-Denis.

Why is it surprising? This ancient vine-growing area is not only famed for its fine wines, but also its natural viticultural approaches. Domaine Ponsot, although neither certified organic nor biodynamic, uses no insectides or pesticides, minimal manipulation of the wine and pays attention to lunar cycles. Nevertheless, Ponsot, who admits: “I am in love with nature,” has opted for a highly technical, synthetic seal. And this is not in an experimental capacity – everything he produces from the 2008 vintage is stoppered with a synthetic cork called AS-Elite by Ardea Seal.

He was inspired to use the closure, above all, because of the variable porosity of natural cork. TCA, he says, like Paul Pontalier in Part 1, is a problem in about one bottle in a thousand, but explains that with very old wines from his domaine, there is great variation in evolution due to the inconsistent oxygen permeability of natural cork. “We might find that of two bottles stored in the same cellar, only one is good because the porosity of cork is different from one bottle to another.”

This inspired Ponsot to search for a solution, and after 20 years of research, he opted for the Ardea Seal. “I looked at all the experiments made at two laboratories [one in Switzerland, the other in Italy] using glass, screwcaps and different kinds of plastic.” It was only the Ardea Seal – made in Italy – which, according to Ponsot, offered the benefits of being chemically inert while guaranteeing a consistent and fixed quantity of oxygen release into the wine.

But how much oxygen does a wine require to gain greater complexity over the long term? For this, Ponsot joined forces with Ardea Seal product developers. “I helped the engineers decide how much oxygen should go into the wine in a given time, and this is new, and incredible.”

To work out an ideal amount, Ponsot tasted thousands of bottles sealed under natural cork. Using a machine to test the quantity of oxygen in a ten-year-old wine, Ponsot found that the quantity of oxygen in wines of this age ranged from 10-350 parts per million (ppm). “We found out that the best wines, with the best taste, had around 100ppm, so we decided, that if possible, we would allow [an oxygen ingression of] 90 to 120ppm over ten years.”

Hence, the Ardea Seal AS-Elite has a polymer section in contact with the wine, and Ponsot compares it to the waterproof and breathable fabric Gore-Tex. “It allows air to go in, but not the wine go out”. Furthermore, “the porosity of this [section of the seal] is calculated in advance, so we know exactly how much oxygen is going into the wine in a given time.”

There’s another aspect which has convinced Ponsot to use the hi-tech synthetic cork, and that is the seal’s resistance to stretching. When the Ardea Seal is pushed into the neck of the bottle, it doesn’t elongate, avoiding the risk of oxygen passing down the sides of the synthetic closure. He also stresses that the polymer in contact with the inside of the bottleneck is adaptive, so it can mould to fit inconsistencies in the glass, although this does mean that the Ardea Seal can be hard to take out.

As for the cost, at €0.35 per closure, the Ardea Seal is less than half the price of the natural corks he was previously using.

Ponsot notes that others in the Côte d’Or are looking on with interest, and “all the big names” are trialling the closure, while fellow Morey-Saint-Denis resident, Domaine David Clark, is also using the Ardea Seal. Elsewhere, he says that Domaine Comte Senard in Aloxe-Corton is now stoppering its wines with Ardea Seal AS-Elite.

“We now have 12 grand crus,” he says, “which make up more than 75% of our production. I would not do anything against them – that’s how confident I am to use it [Ardea Seal AS-Elite].”

The drawbacks? Ponsot says you do need to use “perfect machinery” during bottling.

This profile is an extract from a longer article in the August edition of the drinks businesswhich considered three winemakers and their closure choices, as well as the results of an experiment by Paul Pontallier at Château Margaux, along with views from a range of closure manufacturers.

Click here to read Part 1 – The world’s most high profile experiment?

Click here to read Part 2 – In praise of screwcaps

And click here to read Part 3 – Moving back to cork