Nofima reports

Challenges related to processing and analysis of Norwegian seaweed, focusing on Sugar kelp and Winged kelp

Blikra, Marthe Jordbrekk; Skipnes, Dagbjørn; Noriega Fernández, Estefanía; Skåra, Torstein

Publication details

Publisher: Nofima AS

Issue: 35/2020

Number of pages: 18

International Standard Numbers:
Printed: 978-82-8296-652-8

Open Access: none


Kelp is a new and exciting ingredient in the food industry, restaurants and in the kitchen that is receiving increasing attention, but some of the components in kelp are potentially unfortunate and should be considered when preparing food. In this report, we have focused on the kelp species sugar kelp and winged kelp, and the component iodine - which we need, but in relatively small doses -, as well as the heavy metals cadmium and arsenic which are undesirable.
Several studies have shown that it is possible to remove significant parts of the iodine content from kelp using relatively simple processing methods, such as boiling. There is good reason to believe that newer methods, such as high pressure, ultrasound, and enzyme treatments, have the potential to reduce iodine and heavy metals beyond this level, and perhaps in a more selective way than boiling, which also removes several flavor compounds and nutrients from the kelp.
The amount of iodine in kelp varies depending on various conditions (species, location, season, etc.). As of today, it is difficult to predict the amount of iodine in kelp without analyzing the iodine content in each harvest. In Nofima, we are working to establish two methods, a spectroscopic and a faster method, which can be used for various research purposes related to analysis of iodine in kelp and how we can control the content of iodine.
There are various recommendations for maximum iodine intake. These seem to depend on how much iodine the population initially ingests in their food. There are few guidelines in relation to the content of iodine and heavy metals in kelp, which places demands on the food industry for controlling the contents in each product as well as for establishment of recommended portion sizes.
Based on the research done so far, we have calculated how much sugar kelp can be eaten without exceeding the maximum recommended daily intake of iodine. More than anything else, the result emphasizes the variations. There is great variation both in terms of how much iodine is found in harvested kelp and how much is removed during the cooking process. This provides a great deal of uncertainty regarding the amount of kelp one should eat and reinforces the need for frequent analyzes of specific harvests on the part of the producers, as well as calculation of recommended portion sizes. Nevertheless, it must be acknowledged that there is a need, especially among consumers, to get more clarity on how much kelp is safe to eat.