EFSA has said that alternative methods such as heat treatment could be effective in tackling norovirus contamination in oysters but decided against recommending their introduction over fears the taste and texture changes they produce would be unacceptable to consumers.
Instead the Parma-based agency said ensuring oysters were not produced in faecally contaminated areas was the most effective way of controlling the virus in the shellfish.
The report, EFSA Scientific Opinion on Norovirus (NoV) in oysters: methods, limits and control options, acknowledged but decided against the alternative measures - despite current measures not being effective in reducing the virus.
Organoleptic changes
“Alternative treatments such as commercial heat treatment and high pressure may be effective for NoV inactivation, but give rise to organoleptic changes that may be unacceptable to consumers,” it said.
“Current treatment regimes for products placed live on the market (depuration and relaying) as commonly practiced do not effectively reduce NoV in oysters.”
Current controls against norovirus, such as relaying and depuration, involve the relocation of oysters to uncontaminated areas – neither is very effective against viruses, said the agency.
“Depuration and relaying may be improved by optimising process parameters to enhance NoV reduction (e.g. depuration times, water temperature)."
The scientific opinion, which was produced by EFSA’s Biological Hazards Panel, added that measures should focus on preventing contamination of production areas rather than attempting to remove the virus from contaminated oysters.
FSA backs EFSA
The UK Food Standards Agency (FSA) has backed the EFSA stance on the use of alternative methods.
It told FoodQualityNews.com: “We encourage industry to consider all potential solutions, however acknowledge some maybe be less acceptable to consumers. For example we know thorough cooking destroys norovirus but there is often a consumer preference to eat shellfish raw or lightly cooked,” said FSA spokesperson Brad Smythe.
“We are continuing to work with the UK shellfish industry to reduce the levels of norovirus in oysters and identify a safe limit for consumption.”
Increasing the knowledge we have about how norovirus affects oysters will help the industry to find ways of tackling it and ensure their products are as safe as possible for consumers,” Smythe added.
Virus control doubts
FoodQualityNews.com reported in November 2011 on the FSA’s doubts about purification processes used in oyster production – despite research that found 76% of UK oysters contained norovirus.
“In industry there is currently a very good purification process for the detection and control of bacteria,” a FSA spokesperson said at the time.
“Unfortunately this process is not as good at controlling viruses.”
“Eventually we will look at the purification processes in place to make them more effective in the removal of viruses. But in terms of bringing in the use of specific systems, we are not at the stage to discuss this.”
In 2009, the US Food and Drug Administration (FDA) was forced to back track on its plans to ban the sale of oysters during warm months of the year – when norovirus is most prominent – after pressure from the industry.
