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A New Zealand winery's 4000-case shipment of pinot noir has been rejected by a German company because it said the level of copper in the wine was well over the European recommended limit.
The incident has worrying implications for New Zealand's $700 million export wine industry and has put the spotlight on the use of screwcaps on wine bottles.
It is understood the copper levels in the Te Kairanga pinot noir were 3.6 parts per million (ppm) in a wine that was bottled and labelled specifically for the German customer.
The European Union standard for copper residues is 1ppm.
It is possible other exported wines do not comply with residue levels, as copper is not routinely checked for export certification in New Zealand. Nor is copper checked in wine for sale in the NZ market.
Te Kairanga acting chief executive Ian Frame said the wine did not meet the customer's strict requirements but he was unable to provide details.
He was not concerned about the rejection. "The product is not branded Te Kairanga, and in all the other countries we deal with this is not a problem."
New Zealand Wine chief executive Philip Gregan said he was not worried that the incident would blemish New Zealand wine's reputation internationally. Germany was known as a "stickler for technical points" in the wine world.
"They are just very pedantic about rules and regulations," said Mr Gregan. "If there's an issue that comes out of a customer in Germany, it never surprises me."
Copper is required in small quantities in humans but an overdose can cause serious problems such as liver damage and kidney failure. Less severe overdose symptoms include vomiting and problems with co-ordination or movement.
In the wine industry, copper is often added to wine as it eliminates smelly characters associated with organic sulphur compounds that can form during fermentation and bottle ageing.
Traditionally it is added to bulk wine at very low levels and is filtered out before bottling.
Some industry sources say its use became more common as screwcaps increasingly replaced corks.
"Everybody was adding far too much when they first started using screwcaps," said Bruce Kirk of the food chemical supply company Scios. "That has eased off now, and if anything copper use is going down."
But Lincoln University food and wine group leader Dr Roland Harrison said copper had been used for years and he did not believe there had been a screwcap-driven rise.
* Additional reporting - Keith Stewart
