High pressure processing kills norovirus say researchers
strains in raw foods like shelf fish, according to new research
published in the January 2007 issue of the journal Applied and
Environmental Microbiology.
"This work is the first demonstration that norovirus can be inactivated by high pressure and suggests good prospects for inactivation of nonpropagable human norovirus strains in foods,"the researchers stated in their paper.
Currently, there is no adequate method for treating contaminated shellfish because viruses can remain live for several days, the researchers said.
High pressure processing provides an alternative means of killing disease or spoilage pathogens in many foods without a loss of sensory quality or nutrients. It is a non-thermal pasteurisation process in which a food is subjected to pressures four to seven thousand times higher than normal atmospheric levels. The pressure is held for a time, generally under 10 minutes.
The extremely high pressures inactivate microorganisms. Food processors can maintain the sensory and nutritional quality of their food products by not using additional heating to kill the microsorganisms.
For their study into HPP, the scientists developed a recently identified strain of murine norovirus (MNV-1)in vitro. The virus has more biochemical, pathological, and molecular similarities to human noroviruses than any previously used forresearch, they stated.
In the study MNV-1 was evaluated using HPP at temperatures between 41 and 86 degrees Fahrenheitfor two to 15 minutes .
Their results showed that a five minute treatment using different pressure ranges was sufficient to inactivate the virus at a variety oftemperatures. Inactivation rates of the virus was improved when HPP was also applied at refrigeration temperatures.
"This study also demonstrated that five minutes of high pressure processing at 41 degrees Fahrenheit completely inactivated the MNV-1 strain in oystertissue," the researchers stated.
Norovirus infection is a common problem worldwide with 40 per cent of reported cases in the US alone attributed to food borne outbreaks. Shellfish and produce are twoof the most usual sources of norovirus infections, as uncooked foods can often become contaminated following exposure to contaminated irrigation waters or after human handling.
