Impact of pretreatment on iodine content in Laminaria digitata assessed by inductively coupled Plasma-Mass Spectrometry

• Processing significantly reduces iodine content relative to the washed control. • Blanching and boiling reduce iodine content, while dehydration increases it. • Rehydration partially reverses iodine concentration but still results in iodine loss. • Controlled processing can optimise iodine levels for food safety and nutrition. Seaweeds, particularly Laminaria digitata , are a rich source of iodine, essential for thyroid function, but excessive intake poses health risks. This study evaluates the impact of processing methods, including washing, blanching, boiling, dehydration, and rehydration, on iodine levels to optimise its safe consumption through controlled processing. The washed baseline sample contained 154.5 mg/kg DW (50.2 mg/kg FW) iodine, providing the reference point for calculating percentage reductions and increases. Blanching reduced iodine by 46.1% (1-minute) and 69.8% (3-minutes), while boiling for 20-minutes led to a 49.5% reduction. In contrast, dehydration concentrated iodine, reaching 317.4 mg/kg (20-minutes), 469.8 mg/kg (48-hours), and 473.9 mg/kg (72-hours). Rehydration resulted in a 78% iodine loss from the dehydrated state, likely due to iodine diffusion into the surrounding liquid. A one-way ANOVA showed no significant differences among the processing methods ( P ≥ 0.05 ). However, paired t-tests demonstrated that all processing methods significantly reduced iodine content compared to the washed control ( P ≤ 0.05 ). These findings indicate that processing reduces iodine relative to the unprocessed state, although the magnitude of reduction does not differ significantly between methods. Controlled processing therefore offers a practical approach to moderating iodine intake while maintaining nutritional relevance.