French wine closures giant Oeneo has successfully defended its patent to technology used in its DIAM closure, following a challenge by a coalition of natural cork producers.

Paris-based Oeneo said this week that the EU Patent Office in Munich has upheld the firm's patent on "super-critical CO2" technology, known as the Diamant process and which was developed in coordination with the Government-owned French Atomic Agency.

The technology is used in Oeneo's DIAM wine closure, which has been widely accepted by a number of large wine firms and retailers, including UK supermarket giant Tesco, which uses DIAM on its own-label wines.

A challenge to the patent was brought by the US-based Cork Supply Group and Pedro Gil Ferreira, who is a consultant to natural cork producers and suppliers.

A spokesperson for Oeneo told just-drinks: "For us, it's business as usual. The fact that these guys were trying to get access to the patent shows that the product works."

Oeneo, which has been using the Diamant process since 2003, said that it is "exploring opportunities to share the technology with selected industry partners".

It said the process has been scientifically proven to eradicate detectable levels of cork taint, known as TCA, and other undesirable compounds in wine.