The National Food Institute, Technical University of Denmark has for the Danish Veterinary and Food Administration completed an evaluation on the efficancy of heat treatment to inactivate norovirus in berry products, such as juice and tart. The evaluation discusses which time - temperature combinations that are required during heat treatment of berry products in order to reduce norovirus.
On several occasions Danes have suffered from diarrhea and vomiting after being infected with norovirus due to consumption of contaminated berries. Berries can be contaminated with norovirus during production via sewage polluted growing or irrigation water or by infected food handlers. Norovirus is excellently kept frozen and as berries are often eaten without prior treatment, consumption of frozen berries has often resulted in illness among consumers.
The Danish Veterinary and Food Administration has asked the National Food Institute, Technical University of Denmark to assess which temperature - time combinations that can reduce norovirus in berry products, such as juice and tart. The evaluation has been made in connection with the new legal requirement from the Danish food authority to the food industry that frozen raspberries used as an ingredient must be boiled for at least 1 minute at 100 degrees or treated using alternative methods providing similar inactivating effect of norovirus. Consumers of frozen raspberries are simultaneously recommended to heat treat frozen raspberries before consumption.
Boiling for 1 minute kills norovirus
The National Food Institute has reviewed the scientific literature and estimates that boiling contaminated raspberries at 100 degrees for 1 minute will reduce the level of norovirus sufficiently to prevent consumers from being ill after eating berries.
In some products it can be a challenge to reach a temperature of 100 degrees of the berries during production. In tarts topped with whole frozen berries baked in an oven, the National Food Institute recommends heat-treatment for an extended time period at lower temperature, will adequately reduce the level of norovirus. The National Food Institute estimates that a potential content of norovirus in diluted juice made of frozen berries will be reduced significantly during the additional processing, that heat treatment at 80 degrees for 20 seconds will be adequate.
The evaluation also appoints that the literature within this area of research is most sparse, and that more studies on inactivation of norovirus in different products are much needed.
Read more
See the entire evaluation from the National Food Institute, Technical University of Denmark: Heat inactivation of virus in berry products (pdf, Danish only).
Read more about the Danish Veterinary and Food Administration’s new requirement: Nyt krav om at koge frosne hindbær - "Brug Bærret - men kog det!" (Danish only).