Reduction of total, organic, and inorganic arsenic content in Hizikia fusiforme (Hijiki)

Abstract

This study aimed to evaluate the reduction of total, organic, and inorganic arsenic content in Hizikia fusiforme (hijiki). Initially, the six most common arsenic compounds in hijiki and its organs were evaluated, among which only arsenate and arsenobetaine were detected. Thereafter, the entire plant, including the stalk and leaves, was treated with heat and NaCl solution, individually and in combination. Heating at 90 °C for 5 min significantly reduced arsenic content in hijiki by approximately 33-80%. Treatment with NaCl solution significantly reduced arsenic content in hijiki, except for arsenobetaine content in the stalk. Combinatorial treatment further decreased arsenic content by more than 5-20%. In conclusion, consumption of hijiki after boiling at 90 °C and soaking in 2% NaCl solution reduces the intake of inorganic arsenic by consumers.

Keywords: Heating; Inorganic arsenic; Organic arsenic; Soaking; Total arsenic.

Fig. 1

Effect of heat treatment on arsenic content. Total hijiki, stalks, and leaves were obtained. All samples were heated in water (w/w = 1:10) at 90 °C for 5 min. Total arsenic, arsenate, and arsenobetaine content was determined in total hijiki (A), stalks (B), and leaves (C). Untreated raw hijiki samples were used as the control.# indicates significant differences at p < 0.05 against untreated raw control

Fig. 2

Effect of NaCl treatment on arsenic content. Total hijiki, stalks, and leaves were obtained. All samples were soaked in 0%, 1%, and 2% NaCl solution (w/w = 1:10) for 20 min. Total arsenic, arsenate, and arsenobetaine content were determined in total hijiki (A), stalks (B), and leaves (C). Untreated raw hijiki samples were used as the control. Different letters indicate significant differences at p < 0.05

Fig. 3

Effect of combinatorial treatment of heat and NaCl on arsenic content. Total hijiki, stalks, and leaves were obtained. All samples were heated in water (w/w = 1:10) at 90 °C for 5 min and soaked in 0%, 1%, and 2% NaCl solution (w/w = 1:10) for 20 min. Total arsenic, arsenate, and arsenobetaine content was determined in total hijiki (A), stalks (B), and leaves (C). Untreated raw hijiki samples were used as the control. Different letters indicate significant differences at p < 0.05