Hokkaido University Research Profiles

Manufacturing Technology

Iodine Reduction in Edible Dried Kelp

Hideshi Seki Specially Appointed Professor

Technology to reduce iodine in dried kelp by the competitive adsorption method

We have developed technology that can remove approximately 90% of iodine from kelp by simply circulating and distributing an extraction solvent containing monosaccharides and calcium through a column filled with dried kelp and adsorbents.

Content of research

Iodine is an essential element for humans, but excessive intake of iodine can cause thyroid function problems. The Ministry of Health, Labour and Welfare (MHLW) has set the maximum tolerable dose of iodine at 2.2 mg/day, but only 1 g of kelp (Fig. 1) is enough to reach the maximum tolerable dose, due to its high iodine content. Technology for recovering iodine from seaweed has been available for many years, but there has been no research on developing technology for removing iodine from seaweed for consumption. Figure 2 shows the iodine removal rate (○) and mass loss rate (●) of kelp after circulating and distributing an extraction solvent (100 L) containing monosaccharide and calcium for 20 minutes in a column filled with dried kelp (5 kg) and adsorbent (1.5 kg). Although the extraction solvent was used four times to reduce the cost, an iodine removal rate of 90% or more was maintained.

  • Fig. 1 One gram of dried kelp (cultured for 1 year)

  • Fig. 2 Iodine removal rate and mass loss rate of 1-year-old cultured kelp by this technology

Potential for social implementation

  • ・We believe that it can be applied to the reduction of iodine in foods and supplements containing other edible seaweeds and kelp extracts.

Appealing points to industry and local governments

The competitive adsorption method is a very simple technology that requires only mixing and stirring of materials and adsorbents, and does not only remove iodine but also toxic metals. Since the process can be performed under mild pH and temperature conditions, it is suitable for treating biological materials that are easily denatured by acid or temperature.