Estimation of total and bioaccessible levels of iodine in edible seaweeds of Japan by epithermal neutron activation analysis

Edible seaweeds play important roles as daily source of minerals and dietary fibers for Japanese population groups. It is therefore of interest to estimate the intake of minerals and dietary fibers from seaweeds. Although the levels of iodine can be measured by ICP-MS in liquid samples such as urine and water, it is rather difficult to do the same in seaweeds due to polysaccharides in them. In this study, the following eight edible seaweeds were collected from local shores or purchased from stores. Sea mustard is the most popular edible seaweed in Japan; it starts growing quickly in January until it reaches a height of about 2 m in March. Sea mustards in different growing stages were collected, cut into several longitudinal pieces, freeze dried, and pulverized. Dietary fiber was separated from dried powder by in vitro enzymolysis using α-Amylase, protease, and amyloglucosidase. Portions of dried powder and dietary fiber were irradiated for 1-5 min at the Dalhousie University SLOWPOKE-2 Reactor (DUSR) in Canada or the Kyoto University Reactor (KUR) in Japan. After appropriate cooling time, the 442.9-keV gamma-ray of 128I was used to assay iodine by epithermal instrumental neutron activation analysis (EINAA). Total and bioaccesible iodine levels in eight edible seaweeds are shown