National Research Institute of Fisheries Science, Kanazawa, Yokohama, Kanagawa 236-8648, Japan
Hijiki seaweed, a brown alga Sargassum fusiforme, contains a significant level of inorganic arsenic and so has been suggested to be a high-risk food if regularly consumed. Arsenic is present in seaweed in various chemical forms, with inorganic forms being the most toxic. In order to reduce the risk of inorganic arsenic in seaweed products, this study examined the possibility of removing inorganic arsenic from dried seaweed products. The different chemical forms of arsenic were stably contained in the seaweed during heating and drying processing. To remove inorganic arsenic from the seaweed by food processing, the dried raw materials of seaweed were boiled in seawater. It was found that 86-92% of total arsenic could be removed by boiling in seawater three or four times. After this procedure, total arsenic and arsenic acid contents of the dried seaweed (Test product 1-3) were 8.6-18.6 mg/kg and 0.6-0.9 mg As/kg, respectively. After soaking in distilled water at 20℃ for 30 min, prepared seaweed materials were found to contain 2.0-2.7 mg/kg total arsenic and less than the detection limit of 0.3 mg As/kg arsenic acid. Therefore, this novel method of processing seaweed can be used to reduce the health risk of dietary intake of arsenic from hijiki products.