Simple measures for much better cod
Dedicated researchers have used scientific methods to find out how cod can be cooked to perfection.
Would you like to find out more? If so, click on this link to the publication in the International Journal of Gastronomy and Food Science. Nofima scientists Svein Kristian Stormo and Torstein Skåra have published the article that deals with how to cook the sought-after Norwegian raw produce so that you limit the loss of taste and weight, and maintain a nice consistency.
Alternatively, you can join Svein Kristian Stormo in his kitchen and see him document how poaching time and the addition of salt affect the quality of fresh and delicious cod.
“We are right in the middle of the skrei season, and this raw produce is the best you can get. Just a few simple measures can help us maintain this great quality,” says the Nofima scientist.
The project is part of Nofima’s strategic research project ‘FRESK’, funded by the Research Council of Norway.
People are spending less time in the kitchen
Two major trends are currently emerging in Western European food culture: Increased focus on health and diet, but at the same time a decline in consumer skills in the kitchen.
Professional chefs have enough experience and expertise to calculate the cooking time of cod. However, the typical modern consumer is spending less time in the kitchen and therefore does not know enough about how to prepare different raw produce.
“In this study, the main goal was to find out how to limit cook loss when preparing cod. To achieve this, we used accurate scientific methods to measure temperature, fluid loss and salt content. We also measured sensory characteristics such as smell, taste and texture in order to have a gastronomic approach,” says Svein Kristian Stormo.
The dedicated scientist doesn’t always apply such scientific methods in his kitchen at home. His aim now is to show how most people in their own kitchen can get the best possible results when they ‘boil fish’.
“You shouldn’t boil fish, you know. It needs to be poached. I could leave this great raw produce in well-salted, boiled water for ten minutes, and I am pretty sure it would be perfectly cooked,” says the food scientist.
However, he must document a point, so more regimens need to be tested.
Long time, low temperature – and salt
Cod, like seafood in general, is very sensitive to overcooking.
“It results in cook loss and renders the fish dry and unappealing,” warns Svein Kristian Stormo.
However, perfecting the heat treatment of cod is no magic trick. Time, temperature and salt are keywords when the cooking of fish is to be perfected using scientifically proven methods.
Briefly summarised, the findings in the study are as follows:
- The results clearly show that the poaching time is very critical when preparing cod.
- Long poaching time, even when the temperature is relatively low, will in most cases cause an unnecessarily large cook loss.
- Salt limits cook loss during preparation.
The standard method
It is common practice to cook cod by poaching it in salty water. This is one of the standard methods among chefs and ordinary consumers, and gives a very good result if you really have control of temperature and poaching time.
Today, there are three pans of boiling water on the stove in Svein Kristian Stormo’s kitchen. One without salt in the water, one with a salt content of 5 percent, and one where he will poach fresh cod that has been in brine (equivalent to salt content in the sea; approximately 3.5 percent) for a few hours and then poach it in the same salty water.
“Cod tolerates so much salt that you can hardly have too much salt in the water,” says Stormo.
Three plates of fresh cod in small portions are ready on the kitchen counter. Before they go into the pans of water, each portion is weighed. This is to check the cook loss – i.e. how much of the liquid in the fish is lost during the cooking process. This is where salt plays a key role – as well as boosting the taste experience.
Fish is food that is relatively easy to digest, and can be served raw, like sushi, if the quality is high. However, due to food safety, it is generally a good idea that fish is heated in order to kill any dangerous bacteria. However, excessive thermal stress, i.e. a cooking time that is too long or too hot – or both – really ruins the culinary experience. It affects the taste and experience of eating good food.
“Fish is easily overcooked, and when this happens, it is often perceived as dry and tasteless with a fibrous texture,” says the scientist.
According to literature, fish is adequately cooked when exposed to 63 degrees Celsius for at least 15 minutes.
“For most consumers, the minimum cooking time will be approximately at the point when the muscle denatures. This is when the protein loses its natural shape and the fish appears more white in colour. Most people would say that this when the fish begins to flake,” says the scientist.
This time, the scientist deliberately reverts to serious scientific methodology: All three portions – each in their own ‘salt regimen’ – are heated for 20 minutes.
It is now time for the laypeople to taste: Firstly, the fish that has been in brine. It breaks into delicious flakes on the plate. Tasty and juicy – despite 20 minutes of heat treatment.
The next plate is the one with 5 percent salt in the water.
“That’s pretty good, too,” says the scientist. This fish is also so tasty with great texture that someone without cooking experience wouldn’t reflect on the taste.
Finally, the one with no salt. The astonishing thing isn’t the lack of taste when food is not salted. It is the texture – the consistency – which one really notices.
“It almost becomes fibrous. The fish feels ‘coarse’ in the mouth,” says Stormo.
This is due to the cook loss caused by the lack of salt. Re-weighing the fish tells us how much:
- Fish presoaked in brine lost 13 percent of its weight
- The fish with 5 percent salt in the poaching water lost 16 percent of its weight
- The one without salt in the water lost 19 percent of its weight during cooking.
“Adjusting salt levels is often the last thing you do before eating your meal, which is why most people think of salt as a flavouring. However, salt has a formidable ability to bind water. By adding salt to the fish before the cooking starts, the ability of the fish to retain water will be strengthened right from the start. This reduces cook loss and also the loss of valuable nutrients and flavours,” says Svein-Kristian Stormo.
Sous vide is growing in popularity
Sous vide is a cooking method that has long been commonplace in the food industry, and is now becoming increasingly applicable in domestic kitchens. Svein Kristian Stormo and Torstein Skåra chose this method to scientifically document the results of the heat-treatment of cod.
Sous vide is a technique that involves cooking food in a temperature controlled water bath. The temperature is usually lower in sous vide cooking compared to regular poaching or frying, and the temperature in the water bath is usually set to the optimum cooking temperature of the food in question.
Even when cooking food for a long time, the temperature will never exceed the selected optimal temperature, and sous vide cooking is therefore often referred to as LTLT cooking – low-temperature, long-time.
“Another important aspect of sous vide is that the food is vacuum packed in plastic bags to retain aroma and juice that can otherwise be lost during the cooking process,” says Torstein Skåra, a scientist at Nofima’s Department of Processing Technology.
The scientists say that the sous vide method is a practical way of minimising variations during the trials. In addition, by linking sous vide to a more standard method – simmering or poaching – they tried to bridge the gap between scientific and gastronomic points of view.
Salt gives juiciness and texture
The study shows that if salt is added before cooking, one does not need to be so precise regarding the time aspect when cooking fish. If you are unsure, you can simply poach the fish for a few additional minutes and still get a very good result.
“Although there is a great focus on reducing the total amount of salt in our food, it is important to point out that you do not need to use a lot of salt to achieve a good effect when poaching cod,” says Svein Kristian Stormo.
