Hijiki Seaweed (Hizikia fusiformis): Nutritional Value, Safety Concern and Arsenic Removal Method

This study reported the nutritional components and heavy metals of Hijiki seaweed (Hizikia fusiformis) and investigated the efficacy of aqueous extraction method to remove inorganic arsenic from Hijiki seaweed. Hijiki contained 12.2% of crude proteins, 1.8% of total lipids, 14.0% of ashes, 11.3% of total fiber with dry weight, respectively. The content of protein and ashes were slightly lower than other edible seaweeds including Laminaria japonica, Porphyra tenera, Undaria pinnatifida, Palmaria palmate, while the total fiber was much higher compared with those four seaweeds (6.7-7.8%), which showed more benefits to human health especially to intestines. However, Hijiki contained extremely high amount of heavy metal arsenic (total arsenic: 100mg/kg; inorganic arsenic: 44 mg/kg, dry weight), which might be a major safety concern for human consumption. We developed an aqueous removal method to remove inorganic arsenic from Hijiki. The majority of inorganic arsenic (95.9-96.6%) was removed at optimal condition (50°C, pH 4, 8-12h).The inorganic arsenic content of Hijiki ranged from 0.37 mg/kg to 0.46 mg/kg with wet weight after the treatment and met the hygienic standard for marine algae and algae products.