Does lotifish become jelly? Not your fault, according to mathematical measurements

Does lotifish become jelly?  Not your fault, according to mathematical measurements

For many, lutefisk is part of the Christmas tradition. In restaurants, beautiful, white, firm pieces of fish are served. The disappointment is often too much for the aerobic chef trying to make this happen at home. A long moment in the oven makes the difference between solid fish and jelly.

– says Andreas Carlson, professor of mathematics at the University of Oslo, I have always been fond of lutefisk. – At home we always had lutefisk for Christmas. We were salting and putting it in the oven, and suddenly there was nothing left of it but the skin.

The Professor’s Christmas memories of fish suddenly completely falling apart is something many have experienced. As a mathematician, Carlson realized that the transition from solid fish to jelly is what we call a phase transition. Melting ice or boiling water are other examples of phase transitions. Carlson was curious as to when exactly this would happen. Is it possible to find the right time for the fish to come out of the oven?

Carlson contacted one of the country’s top lutefisk experts, Eric Lilibeau, who runs, among other things, Restaurant Code and Vaaghals.

What do you think when a mathematician calls you?

– yes! I’ve been endlessly annoyed at the quality of Norwegian Lutefisk for many years, says Lilbo.

A good lutefisk should be consistent

Lilbo produced between 150 and 160 tons of Lutefisk during his career as a chef at both Theatrecaven and Gamli Radhouse Restaurant. In addition, he ran a number of tests on lutefisk in the run-up to Christmas. His characterization of the quality of the store’s fish is discouraging:

– Even when I put all my experience, love, and care about lutefisk into the business, I never get more than 20-30 percent to maintain a quality that I can vouch for. My hypothesis is that the fish they use are very small, he says. – Because it’s cheaper.

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No one wants to spend time and money on something they can’t achieve or eat something that isn’t good. Lilbo fears that the Lutefiesque tradition is in danger of dying out because of this. Mathematician Carlson says he’s always liked lutefisk, but it’s only now that he’s realized what a really good lutefisk is:

– It’s only in recent years that I’ve seen the look and feel of what a good lutefisk should be.

Lilibeo, for his part, says he fears people will think Lutefisk must be jelly.

So he was very excited about the opportunity to participate in the research.

Find the perfect recipe

The scientist and chef had many hypotheses about what might affect the consistency. Primarily, they wanted to test the cooking time, temperature, and amount of salt, as well as where the fish fillets came from. To make sure they got reproducible results, they were very careful about the raw materials they used in their research. All the fish were from Brodrene Berg from Væroy.

Andreas Carlson (tv), Atle Jensen, Eirik Strøm Lillebø and Torstein Sæter in front of a rheometer measuring lutefisk properties. Photo: Elina Melteig/UiO

What they found surprised them. At first, Carlson thought they would be able to find the point at which the fish turns into jelly, but despite trying hard to make the fish fall apart, they couldn’t. All differences in cooking time, temperature, and salting have little effect on consistency. something jarring. The only thing that seemed to affect the outcome was where the sample was taken on the fish.

They said good food couldn’t be made with inferior ingredients.

It turned out that the tail pieces, that is, the smallest pieces, acquired a touch of jelly consistency when fried for a long time. On the other hand, large pieces were not overcooked, even when the cooking time was doubled or the temperature was increased.

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Size is important

Size is what matters, quite simply, says Lillibeau.

For the seasoned chef, it’s finally possible to get to the table with the facts. And he was correct in his hypothesis.

“Using dried fish that’s too young destroys a thousand-year-old tradition,” Lilbo claims.

He thinks the portions sold in regular grocery stores are too small. He hopes the producers will contribute to the best bits being sold as lutefisk at home in Norway.

– The only thing we use dried fish in Norway is lutefisk, the rest is exported. If restaurants were the sole carriers of Norwegian food culture, this tradition would die, Lilbaugh says.

Thus, imitation will eventually die out because no one can really make it so good. It’s a shame, he says, because now they can prove that raw materials are the reason no one can make it like the restaurant. At the same time, he is glad that so many people are choosing to take lutefisk over them.

When is lotif fish delicious?

To measure the consistency of lotif fish, the researchers used something called a rheometer. This is a device that can measure how a material or fluid responds to pressure, expansion, and bending.

When is lotif fish delicious?

“It has to flake off, it has to be a solid piece,” says Lilboe. These shouldn’t be, but they have a good texture and are a little tougher than fresh fish. A good lutefisk is all about consistency.

– But what is perfect consistency?

“It’s hard to measure perfect consistency,” says Carlson. – But we did find an area where it has the characteristics that Lilbo suggests.

Large slices were in the 6,000 to 10,000 Pa (Pa) range. Pascal is a unit of measurement that indicates pressure per square metre. In this context, it says something about the toughness and tension in a fish when under pressure. On the other hand, the small slides were from 2,000 to 6,000 Pa. Hence it is softer.

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Researchers tips to improve lutefisk

To prevent the small pieces from turning into jelly, you can thus lower the temperature. 60 degrees in a steam oven has become the new recommendation. Previously, the temperature of lutefisk was set at 100 degrees in a steam oven.

“What we’re seeing is that high quality stands in the oven,” says Lillibeau. The lower the temperature, the more control you have. Temperatures drop more slowly, and what goes slowly usually goes well.

Researchers recipe

All fish were washed and then salted. It rested for 45 to 100 minutes before being roasted in a steam oven. Then they verified that the difference in this interval did not affect the consistency.

The amount of salt varied from standard to zero. The temperature varied from 60 to 130 degrees, and samples were taken along the way.

At Gamle Raadhus, the fish is fried for 12 minutes at 100 degrees in a steam oven, but in the experiment, these factors varied.

The salt didn’t seem to affect the consistency at all, but still that’s a lot to say. in Research article Unsalted cuts tend to appear translucent, the researchers wrote, even after they’ve been fried.

Take as much salt as you think you should have, and then multiply it by three, Lilipo advises.

However, some questions remain unresolved. One is about whether vacuum packaging could be one of the reasons why store-bought fish turn more easily into jellies? The researchers can’t answer this time, but it’s safe to hope they dig deeper into the problem.

The article was first published on

Dalila Awolowo

Dalila Awolowo

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