The Norwegian Scientific Committe for Food Safety (VKM) has on request from the Norwegian Food Safety Authority assessed to what extent the Fish Silage Processing Method (FSPM) contributes to the reduction of microbiological risk for category 2 and 3 material of fish origin.
Category 2 material of fish origin is mainly dead and clinically ill fish without outer signs of disease.
Category 3 material comes from fish that has been allowed slaughtered for human consumption and can be used as feed for food-producing animals after treatment.
The background for the request is that the Norwegian Sea Food Federation (FHL) has applied to the Norwegian Food Safety Authority for the right to use end-products from category 2 material treated via the FSPM for agricultural fertilizers, biofuels and feed for fur-, zoo-, pet and circus animals.
The Food Safety Authority also wanted an assessment of the treatment methods for the use of animal by-products of category 3 material in feed for farmed fish.
By using the FSPM, animal by-products from fish are minced and acidified to pH 4 or lower and stored for a minimum of 24 hours. The silage is then treated until the particle size is below 10 mm, before it is heat-treated at at least 85 °C in at least 25 minutes. Finally it is filtrated.
Treated fish silage can be further processed to fish oil, protein water and protein concentrate. Processed fish silage and protein concentrate are covered by the definition of fish meal in the by-product regulations.
VKM concludes that the FSPM will reduce the microbiological risks (Clostridium perfringens, moulds, Saprolegnia, parasites and virus) that have been assessed, with the exception of mycotoxins and prions from fish.
However, it has not been proved that mycotoxins from fish poze a health risk to animals or people, and it is unlikely that prions from fish will do so either.
Regarding category 2 material from fish cultivated in earth ponds where dead fish are not removed daily, the concentration of C. botulinum may reach concentrations so high that the possibility of spores of C. botulinum
type E surviving heat treatment cannot be ruled out. However, spores surviving heat treatment will not germinate (transform to ordinary bacteria) as long as pH ≤4.