Can cod sperm be used for anything other than making new ‘cod babies’? Absolutely! Using modern extraction methods, cod milt can become new, valuable products such as oil and protein powder – which in turn can become both food and beauty products.

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Anne-May Johansen  

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Cod milt is also considered a delicacy in some culinary circles, but we won’t explore that avenue in this article. The focus here is on creating products from cod sperm using hydrolysis. 

Migrating skrei are full of roe – and milt

In the winter, the long-awaited migrating skrei are racing towards the northern Norwegian coast to spawn. The female fish are full of roe, which is a key part of the Norwegian dish skreimølje, and is also industrially utilised in caviar, canned goods and other food products for human consumption. 

However, male cod are just as full of the other constituent that is required in order for cod spawning to result in new generations of cod: Milt – the sperm or semen of the fish. 

However, finding a good use for cod sperm has proved a bit more challenging. 

Birthe Vang leads the work in which Nofima, NTNU, Nuas Technology and Nord-Senja Fisk collaborate on the use of new technologies to increase the utilisation and value of cod milt. Photo: Rune Stoltz Bertinussen, Nofima

Value added for the Norwegian whitefish industry

In the research project Cod Milt –  Oil and Protein Processing (TOPP), the goal is to develop and improve hydrolysis processes in order to make new, valuable cod milt products. Enzymatic protein hydrolysis is a process of splitting proteins with the help of enzymes. Enzymes act as a kind of ‘scissors’, which cut larger proteins into small water-soluble proteins. These water-soluble proteins are called peptides and can then be dried into a protein powder. 

“We will test the peptides from cod milt for health-promoting effects related to lifestyle diseases,” says Nofima scientist Birthe Vang. She is the project manager of TOPP.

Project partners include Nuas Technology, which has developed a portable hydrolysis plant with patented hydrolysis technology, the Norwegian University of Science and Technology (NTNU), which will work on the evaporation and separation of hydrolysate, and the fish production company Nord-Senja Fisk AS, which is a supplier of cod milt. 

The work is being funded by the Norwegian Seafood Research Fund (FHF). 

“In order to understand the value creation potential of whitefish offal using methods such as hydrolysis, we must be able to acquire increased knowledge in the field. With the knowledge presented in the project, we will be able to create added value for the Norwegian whitefish industry and contribute to increased value for the entire raw material,” says Birthe Vang.

Other participants in the project are Kjersti Lian, Marte Jenssen, Tone Aspevik, Sileshi Wubshet and Åge Oterhals from Nofima, Frode Blålid from Nuas Technology, Ignat Tolstorebrov from NTNU and Egil Johansen from Nord-Senja Fisk. 

Portable plant

Annually, approximately 70-80 tonnes of cod milt are landed in northern Spain. Of this, high-quality milt goes to human consumption on the Asian market, and the remains are used for silage, which is then turned into feed. 

Developing new cod milt products will represent a significant increase in raw material value. In the future, this increase in value could literally take place on the quayside, as the TOPP project is going to test a compact and portable hydrolysis plant that can be placed where the raw material is landed. 

“With the support of Innovation Norway, Nuas has built an industrial-scale pilot plant with a capacity of two tonnes of rest raw materials per hour. This plant will now be moved to Senja and put into production,” says Vang.  

Nofima currently operates the Biotep national pilot plant in Kaldfjord on the outskirts of Tromsø for what is called marine bioprocessing. Both scientists and operators at the institute have thus gained a great deal of knowledge and expertise regarding all phases of the utilisation of marine rest raw materials. The combination of NTNU’s cooling and handling expertise at the Department of Energy and Process Engineering (EPT), the technology from Nuas, and cod milt from northern Spain means that all the pieces are in place to gain a significant increase in value from the raw material. 

“Enzymatic hydrolysis is not a new technique. What is special about this project?”

“If the use of compact and portable hydrolysis plants is to become a reality for the industry, we must have knowledge about how these mobile processes can be carried out efficiently. One of the most useful things for the industry partners involved in the project will be to show that it is possible to move the plant around and develop a gentle, specially adapted way of processing the rest raw material,” explains the Nofima scientist.

TOPP is a 2-year project and the scientists have already started laboratory work. It is important that the methods are tested on a lab scale before they are scaled up to an industrial scale at Nuas Technology. The results from Nuas’ test production at the Botnhamn fish reception facility at Senja will be introduced to potential customers for testing. 

“We are excited about the results of the project,” says Birthe Vang

She believes that a successful project will increase the possibilities regarding the utilisation of cod milt for human consumption and other value products. 

“This is in line with the Government’s bioeconomy strategy, which has “More sustainable and efficient resource utilisation” as one of three primary goals,” she says.

Photo of scientist Birthe Vang in the laboratory
In the laboratory at Nofima in Tromsø, the hydrolysis of cod milt is tested using water-soluble enzymes. The aim of the TOPP project is to scale the process up so that it can be carried out directly where the fish are landed using compact, portable hydrolysis plants. Photo: Anne-May Johansen, Nofima

Facts about cod milt

  • Milt is a common term for male fish sperm/semen.
  • Currently, the best quality cod milt (fresh and light) goes to human consumption, mainly used in sushi on the Asian market. 
  • The rest mainly goes to silage, which is then turned into animal feed
  • Like many other marine raw materials, cod milt contains good-quality proteins and fats that have many possible uses, the highest paying of which are human consumption and pet food. 
  • Cod milt is also known as a source of DNA, and a small volume of cod milt is currently used for the production of nucleic acids.

Source: Great Norwegian Encyclopedia and Nofima

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