PhD defence by Randi Sund

Principal supervisor:

• Associate Professor Susan L. Holdt (DTU Food)

Co-supervisors:

• Senior Researcher Claus Heiner Bang-Berthelsen (DTU Food)
• Associate Professor Dagbjørn Skipnes, Nofima, Norway
• Researcher Pierrick Stévant, Møreforskning, Norway

Examiners:

• Associate Professor Aberham Hailu Feyissa, DTU Food
• Professor María Guðjónsdóttir, University of Iceland Associate
• Professor Fredrik Gröndahl, KTH, Sweden

Chairperson at defence:

• Associate Professor Nina Gringer, DTU Food

Resume
Seaweed is gaining popularity as a sustainable and nutritious food source. Its cultivation requires no land area, fresh water, or fertilisers. It contains nutrients such as protein, fibre, and essential minerals, as well as bioactive compounds that can provide the consumer with beneficial health effects. In Norway, seaweed cultivation is expanding, with the species winged kelp (Alaria esculenta) and sugar kelp (Saccharina latissima) as the main species. However, before seaweed can become a regular part of our meals, some hurdles need to be overcome.

One challenge is that seaweeds accumulate compounds from the ocean, including potentially toxic elements like arsenic, cadmium, mercury, lead and iodine. While iodine is essential in small amounts, too much can be harmful. Seaweeds also deteriorate quickly after harvesting, making preservation necessary. To provide a safe and nutritious product, we need to process the seaweed to reduce the concentrations of potentially toxic elements and stabilise the raw material, while retaining its nutritional value and flavour.

In this PhD project, different processing methods were tested for their effects on these two common Norwegian kelp species. Methods tested were warm water treatment, freezing, fermentation, ultrasound, and pulsed electric fields. The effects were studied both in the raw seaweed and when used in a common food (fish patties). The results showed that most methods can significantly reduce iodine and arsenic levels, while cadmium, mercury, and lead levels are increased. Protein levels were also increased after processing. Using seaweed as an ingredient in fish patties increased their iodine levels without affecting taste or texture. This research brings us one step closer to using locally cultivated seaweed as a healthy, safe, and sustainable food source.

A copy of the PhD thesis is available for reading at the department.