Estimation of Arsenic Bioaccessibility in Edible Seaweed by an in Vitro Digestion Method

Overview

Laparra and colleagues measured total arsenic (AsT) and inorganic arsenic (AsI) in three edible seaweed products purchased in Valencia, Spain, then applied an in vitro gastrointestinal digestion method to estimate bioaccessible arsenic. The occurrence-relevant data are the raw/cooked seaweed concentrations and the bioaccessible fractions, all reported on a dry-weight basis. The paper keeps AsT and AsI distinct throughout.

Key numbers

Table 2 reports total and inorganic arsenic in seaweed as µg g-1, dw (mean values ± SD, n = 3). No unit conversion was performed.

For raw seaweed, the source states that AsI represented 0.4% of AsT in Porphyra sp., 20% in Enteromorpha sp., and 55% in H. fusiforme. For cooked H. fusiforme, the source reports cooking-water concentrations of AsT 4.6 ± 0.2 µg mL-1 and AsI 3.7 ± 0.1 µg mL-1; losses referred to seaweed were AsT 45.6 ± 1.6 µg g-1 seaweed and AsI 32.0 ± 0.5 µg g-1 seaweed. Cooked H. fusiforme AsI was 47% of AsT.

Table 5 reports bioaccessible arsenic contents in raw and cooked seaweed as µg g-1 Seaweed, dw (mean values ± SD, n = 6-10):

Table 6 reports bioaccessibility percentages as [(AsT or AsI in bioaccessible fraction)/(AsT or AsI in seaweed)] × 100 (mean values ± SD, n = 6-10):

Method optimization/context values:

• Table 3 shows that H. fusiforme sample weight changed bioaccessible AsT/AsI results: 2 g gave AsT 83.6 ± 2.0 and AsI 48.2 ± 2.6; 5 g gave AsT 61.9 ± 2.0 and AsI 40.6 ± 2.0; 10 g gave AsT 32.8 ± 2.5 and AsI 20.3 ± 1.2, all in µg g-1 Seaweed, dw.
• Table 4 reports six-session digestion precision for raw H. fusiforme: mean concentration AsT 75.9 ± 8.9, AsI 46.3 ± 5.7, and RSD 12% for both, in µg g-1 Seaweed, dw.

Methods (brief)

The study analyzed brown seaweed H. fusiforme (hijiki), red seaweed Porphyra sp. (nori), and green seaweed Enteromorpha sp. (green nori flakes) purchased in Valencia health-food stores. Samples were analyzed as sold. H. fusiforme was also boiled in water at 100 °C for 20 min using 30 g seaweed and 500 mL water; Porphyra sp. was baked at 200 °C for 5 min; Enteromorpha sp. was not cooked because the label recommended raw consumption.

The in vitro digestion used 5 g seaweed with pepsin at pH 2, followed by pancreatin-bile extract at pH 7.2, incubation at 37 °C, and centrifugation at 15 000 rpm for 30 min at 4 °C. Total arsenic was measured after dry-ashing by flow-injection hydride-generation atomic absorption spectrometry (FI-HG-AAS). Inorganic arsenic was determined by acid digestion, solvent extraction, and FI-HG-AAS. Quality control used Fucus sp. IAEA-140/TM, BCR 60 aquatic plant, and BCR-279 sea lettuce certified/reference materials.

Related evidence

• Seaweed/kelp foods (nori, wakame, kombu, dulse — as food products)
• Seaweed
• Arsenic, Total
• Arsenic, Inorganic

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