Bioaccessibility of inorganic arsenic species in raw and cooked Hizikia fusiforme seaweed

Samples of Hizikia fusiforme edible seaweed, a commercially available dried food with high concentrations of total arsenic (t-As) and inorganic arsenic (i-As), both raw and cooked (boiling at 100degreesC, 20 min), were selected for the bioaccessibility study. Cooking caused a significant reduction in the concentrations of t-As (30-43%) and i-As (46-50%), despite which the i-As contents in the cooked product were high (42.7-44.6 mug g(-1) seaweed). An in vitro gastrointestinal digestion (pepsin, pH 2, and pancreatin-bile extract, pH 7) was applied to the seaweed to estimate arsenic bioaccessibility (maximum soluble concentration in gastrointestinal medium) of t-As, i-As, arsenic(III) and arsenic(V). The influence of the gastric and intestinal stages of the in vitro digestion method was evaluated. The gastric stage is the key stage in the solubilization of both t-As and i-As. The bioaccessible i-As in raw seaweed (54.0-66.5%) increases after cooking (78.3-84.4%), a fact that is considered to be of interest because this is the usual form in which this seaweed is ingested. Speciation of the i-As in the bioaccessible fraction revealed a different arsenic(III)/arsenic(V) relationship in the product when raw or cooked. When raw, the majority species was arsenic(III) after either the gastric or the gastrointestinal stage, whereas in the cooked product it depended on the batch analysed, with bioaccessible arsenic(III) contents of 7.1-25.4 mug g(-1) of dried seaweed, which represents 5-17% of the i-As tolerable daily intake. Copyright (C) 2004 John Wiley Sons, Ltd.