Effect of Temperature on the Diminution of Retained Arsenic in Dried Hijiki, Sargassum fusiforme (Harvey) Setchell, by Water-Soaking

摘要

市販乾燥ヒジキ（Sargassum fusiforme（Harvey）Setchell）に含まれるヒ素は，調理前処理として乾燥ヒジキを水に浸し一定時間水戻しすると溶出されてくる．浸漬水の液温を0℃,15℃,30℃,45℃,60℃,75℃,90℃とし，各々浸漬時間を20分,40分,60分,180分,360分に設定して溶出ヒ素量を定量した．同時に，膨潤ヒジキ画分のヒ素含量も定量した．ヒ素の定量は熱中性子放射化分析によった．乾燥ヒジキを75～90℃の浸漬水で水戻しすると，20分以内に総ヒ素量の約70％が溶出されて膨潤ヒジキ中には約30％が保持されている．この内ヒジキ固形物に結合されているのは約10％である．45℃で水戻しを行うと20分以内に総ヒ素量の約60％が溶出され，約40％が膨潤ヒジキ画分に残存するが，この時ヒジキ固形物中に結合するヒ素は総ヒ素量の20％以下である．なお，ヒ素溶出の機構が単一ではないことが推察された．%Arsenic levels in the sea weed, Hijiki, Sargassum fusiforme (Harvey) Setchell, after soaking in water were determined by thermal neutron activation analysis. Commercial dried Hijiki was soaked in purified water for periods of time (20-360 min) at various temperatures (0-90℃). Arsenic concentrations retained in the swollen Hijiki tissues and those dissolved in the aqueous solution were determined. At temperatures higher than 30℃, about 70% of the total arsenic was removed from the swollen Hijiki after discarding the soaking water. The non-extractable arsenic bound to the tissues seems to be about 10% of the total, when estimated at higher temperatures (75 and 90℃). To remove arsenic as much as possible before cooking, it is recommended to soak commercial dried Hijiki in warm water for more than 30 min and discard the water extracts.