The effect of drying process on undervalued brown and red seaweed species: elemental composition

The infuence of drying (sun-drying and shade-drying) on the elemental composition of two brown seaweeds (Treptacantha abies-marina, Cystoseira humilis) and two red seaweed species (Asparagopsis armata and Asparagopsis taxiformis) harvested in the Faial Island (Azores Islands, Portugal) was assessed. The contents of sixteen nutritionally and toxicologically relevant elements were determined: sodium (Na), magnesium (Mg), phosphorus (P), sulphur (S), potassium (K), calcium (Ca), chromium (Cr), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), arsenic (As), bromine (Br), cadmium (Cd), iodine (I), and lead (Pb). While the most abundant macroelement in T. abies-marina and C. humilis was K (64.1–71.0 g kg−1 dw), for both Asparagopsis species, this position was held by Na (85.6–115.3 g kg−1 dw). Iodine content did not surpass 0.1 g kg−1 dw in the brown seaweeds and varied between 4.6 and 5.7 g kg−1 dw in Asparagopsis species. The I Dietary Reference Intake may be ensured by less than 1 g of dried A. armata or A. taxiformis per week. For T. abies-marina and C. humilis, 10.5 g or more of dried seaweed per week may be required. However, excessive I can be a health risk: 1–2 g of dried A. armata or A. taxiformis per week may result in I-related health risks. Moreover, there are As-related health risks for the consumption of C. humilis and, especially, T. abies-marina. The type of drying did not show a clear efect upon the elemental composition.