Adequate heat treatment provides safe fish feed
Report no: 2012: 14
The Norwegian Scientific Committee for Food Safety (VKM) has conducted a risk assessment regarding processing requirements to ensure that fish meal and oil originating from clinically healthy farmed fish does not constitute a risk of infection if it is fed to farmed fish of other species.
The assessment is conducted at the request of The Norwegian Food Safety Authority (NFSA). Present processing requirements by NFSA recommend heating of the by-products, fish meal and fish oil at 85° C for 25 minutes. Based on new data, the fish farming industry requests that the requirements will be lowered to 76° C for 20 minutes for raw materials from aquaculture.
Heat treatment at 85 ° C for 25 minutes
After heat treatment of the by-products of farmed fish and fishmeal derived from such materials at 85 ° for 25 minutes, the probability of presence of all viruses, bacteria and parasites assessed is negligible. After heat treatment of fish oil originating from such materials, the probability is negligible for the viruses and parasites assessed. VKM does not have sufficient information to assess the probability of presence of bacteria in fish oil after such treatment.
Heat treatment at 76 ° C for 20 minutes
If the by-products of farmed fish are heated to 76 ° C for 20 minutes, the probability of the virus spices Infectious pancreatic necrosis (IPN) and possibly also Piscint reovirus (PRV) being present is considered to be low, and negligible for all other viruses and parasites assessed.
After equivalent heat treatment of fish meal and oil originating from such materials, the probability of presence of IPN and possibly PRV is considered to be low, and negligible for other viruses and parasites assessed.
VKM does not have enough information to anticipate the probability of presence of bacteria in fish oil after treatment at 76° C for 20 minutes.
VKM anticipates that ensiling of by-products with organic acid equal to ph value 4 or lower will inactivate some virus species and most bacteria and parasites assessed.
Indicators for inaktivering of viruses and bacteria
IPN virus appears to be more heat resistant than the other fish pathogens assessed. VKM believes that this makes the IPN virus to a suitable indicator for testing methods of heat inactivation
VKM proposes that NFSA also should consider using a bacterial indicator. Bacteria have more protective stress mechanisms than viruses, and a virus may not be a suitable indicator for effects on bacteria in all situations.
There is a lack of information on the effects of heat and acid tolerance of some of the pathogens assessed, among those for PRV, and uncertainty is associated with some of the reviews.
The risk assessment
NFSA is going to apply the risk assessment in its work on regulations of fish feed. The salmon production in Norway generates about 195 000 tons residual raw material a year (2009), which may represent about 65-70 000 tons of fish meal/oil (statement from the industry).
VKM´s Panel on Animal feed is responsible for the risk assessment, which is prepared by an ad hoc expert group.