Norovirus-free oyster breakthrough

The fishery blamed for the outbreak of food poisoning at Heston Blumenthal's Fat Duck in 2009 has developed a system which it says can now guarantee norovirus-free oysters.

Colchester Oyster Fishery believes its Pyfleet Pure method is a world first, in that the process can guarantee oysters can be sold to operators without any trace of the common stomach bug.

"In 2013 I spent three months going through all the literature on norovirus and oysters and it became clear to me there was a way of removing the norovirus from the oyster," Woodage explained. "That needed to be tested so I contacted Colchester Oyster Fisheries who have been supportive of my experiments."

He spent six months taking oysters, infecting them, and using various techniques to remove any traces of norovirus. His research has been supported by government laboratories and Public Health England and is verified by a UKAS accredited laboratory.

The final method is a closely guarded secret, but it is a natural process that triggers the oyster to remove any norovirus without any impact on the quality of the bivalve.

Colchester Oyster Fishery managing director Paul Harding said: "We've taken the worst oyster you could ever find out there and doubled the rate of norovirus, and our system will still clear it."

The system adds an extra four or five days to the depuration process, but will not affect the freshness of the oysters since they are alive and in sea water the entire time.

Harding said that the fishery had been supplying the Pyfleet Pure oysters to operators for the past six months as it has been proving the concept.

He said: "The system is proven, the EHOs are behind it and there is the certificate to prove we've tested the system. We don't need to but we'll carry on testing every single batch so that if any restaurateur has a problem they can prove a guest wasn't made ill from an oyster."

The Pyfleet Pure proccess will carry a 10p premium per oyster, taking the cost to around 65-70p for operators.

The Pyefleet Pure process

If contaminated oysters are moved into uncontaminated sea water, the amount of norovirus in their tissues gradually decreases.

"Oysters are able to thrive even in contaminated sea water and have evolved a natural biological mechanism to remove contaminants, including norovirus, from their tissues," Woodage said. "My research identified how this biological mechanism works and the new purification process provides the optimum environment for it to take place."

The system quickly removes any norovirus that has been accumulated by the oyster without the oyster even being aware that this is happening. It adds around four days to the depuration process, taking oysters to six or seven days of processing before distribution.