Ensuring safe and tasty rakfisk

Rakfisk - freshwater fish preserved in a traditional way by fermentation - is becoming more and more popular in Norway and the producers want to find out more, both about food safety and how the special taste and consistency develops.

Contact person
Portrettbilde av Lars Axelsson
Lars Axelsson

Senior Scientist
Phone: +47 901 57 584

Rakfisk is a traditional Norwegian food, but what happens to the fish during the process is not well understood.

“Few scientific studies have been made of rakfisk. That’s what we intend to put right with this project. We are aiming to investigate both how and why bacteria develop during fermentation and maturing,” says project manager and senior adviser Hans Blom of Nofima Mat AS.

Getting help from genetic technology

In the 1970s, the Norwegian Institute for Food Research described the safe levels for salt content and temperature for Clostridium botulinum. The salt content should be higher than 4.5 per cent while the temperature should not exceed seven degrees. In the 1990s Nofima Mat (then called Matforsk) established a product development network of rakfisk producers in Valdres with a view to brand building and hygiene routines in production. Some microbiological studies were done at the time and we know that a special type of lactic acid bacteria plays a vital role in the process, but knowledge is still very limited.

“In the research project now being started we will use genetic technology methods to analyse complex microbial communities, an established technique developed at Nofima Mat. We will eventually be able to determine limit values for dangerous bacteria and not least investigate how the bacterial flora develop. We will be collecting fish and brining solution from the producers frequently and regularly so that we can closely follow bacterial development,” explains senior research scientist Lars Axelsson of Nofima Mat.

Rounded and mild or strong and tangy

As well as looking at the bacterial flora from a food safety point of view, the researchers will be carrying out sensory analyses and will investigate how the bacteria affect taste and consistency.

Various kinds of fish are currently used to make rakfisk. Some producers use farmed Arctic char, others use farmed trout and others use wild trout. One important question is whether the choice of fish species has any significance for taste and consistency or whether it is the process itself that makes the difference.

“Based on current experience, we assume that the differences in taste and consistency are due to conditions such as temperature, salt content and how long the fish lies in the solution. But we have never investigated this scientifically before and we want to see what significance the fish species might have for taste and consistency,” says Blom.

Identifying market opportunities

Rakfisk is primarily a seasonal product at present, but this season can be extended in the same way as have the seasons for other Norwegian specialities, like akevitt and lutefisk for example.

“For example rakfisk based on wild fish can be sold year round, and it will be less of a job to make safe rakfisk from winter fish. Moreover, with fermentation and maturation processes that ensure safe and consistent quality, there is nothing to stop producers making and selling top quality rakfisk all year round,” concludes Blom.

The board controlling research funds from the Agricultural Agreement has granted funding for the research project. 52.5% of the project costs are being contributed by the rakfisk producers themselves.

Food safety and quality  

Related content