New Method for Continuous Measurement of Core Temperature in Fish Cakes

At Lerøy Seafood’s factory in Stamsund, they produce 160,000 fish cakes per shift. During peak season, they run two shifts. 

Currently, there is no commercially available method to continuously measure and control the core temperature. Now, scientists from Nofima and SINTEF Digital are testing whether a spectroscopic measurement method based on NIR (near-infrared) spectroscopy can contribute to better control and more consistent quality. 

Balancing Food Safety and Taste 

Each cake must have the correct temperature to be safe to eat. The core temperature must be at least 72°C to kill potential pathogenic bacteria, but if it gets too high, the fish cakes lose flavour and become too dry. This can be a challenging balance in large-scale production. To be on the safe side, producers often choose to maintain a higher temperature than necessary. 

“With continuous measurements, we can see over time how the core temperature varies throughout the day, week, and month. We can use the findings to optimize the process so that the core temperature becomes more stable. This will give us fish cakes with more consistent quality,” says Steffen Andersen at Lerøy. 

From Trials at Nofima to the Factory in Stamsund 

The development of the new measurement method started in Nofima’s Meat Pilot Plant. Here, Meat Specialist Tom Johannessen made fish cakes according to Lerøy’s recipe. These were cooked at different temperatures and cooking times to achieve various core temperatures. 

Then, scientists measured the core temperature with both a traditional insertion thermometer and the NIR sensor. 

“We compared the NIR measurements with traditional thermometer measurements and found a very good correlation. The promising results made it natural for us to proceed with larger-scale testing at the Lerøy factory,” says Jens Petter Wold, senior scientist at Nofima and director of SFI DigiFoods. 

Measuring Deep Inside the Product 

The NIR sensor was mounted on the production line in the factory, above the conveyor belt where the fish cakes come out of the oven. It can measure the temperature in each fish cake that passes. The special thing about this NIR technology is that it can measure right to the core of the product. 

To get accurate measurements, it is important to measure in the right place. The temperature of a single fish cake coming out of the oven can vary greatly. The temperature at the edges can be 8-10 degrees higher than the temperature in the middle, so it is important to measure in the centre of the cakes, where the temperature is lowest. 

Reducing Waste and Saving Energy 

Today,operators regularly insert thermometers into samples of fish cakes. This is not only time-consuming, but it also destroys the products being measured. With the new technology, Lerøy can continuously monitor the temperature without wasting a single fish cake. 

There can be waste if the core temperature of the fish cakes does not reach 72°C.  
“If the temperature is too low, and we discover it quickly, we can heat them up again, but if the fish cakes have already been sent for cooling, it is too late, and then there is waste,” says Steffen Andersen at Lerøy. 

The Future of Food Production 

The project shows how new technology can improve traditional food production. The same principles used for fish cakes can also be applied to other heat-processed foods like burgers and steaklets. A limitation here is that the products cannot be too thick, as there are limits to how deep we can measure with NIR. 

“Using this type of technology is not just about making production more efficient. It is also about producing safer food with better quality and less waste,” concludes Jens Petter Wold. 

Contacts

Jens Petter Wold

Senior Scientist

Tom Christen Johannessen

Meat Technologist

Lars Erik Solberg

Scientist