Proximate Composition, Physicochemical and Microbiological Characterization of Edible Seaweeds Available in the Portuguese Market.

Background: The aim of this work was the study of the proximate composition and profile of fatty acids, minerals, and some microbiological aspects of four edible seaweed species (, , sp., and sp.) available in the Portuguese market for food consumption, and produced in a national Integrated Multi-Trophic System (IMTA).

Methods: Moisture, ash, and total lipids were determined gravimetrically. Crude protein was analysed by Duma's combustion procedures. The total carbohydrate content was assayed by the phenol/sulphuric acid method. The assessment of the fatty acids methyl esters (FAMEs) was determined through GC-MS. Characterization of elemental analysis was performed by ICP-AES. Different standard microbiological methods were applied for microorganisms. Statistics were performed using the non-parametric Mann-Whitney U test to assess significant differences between samples.

Results: Lipid contents ( = 3) were very low (1.6-2.3%), particularly in , and (1.6-1.7%). The protein content ( = 4) varied from 14.4% in to 23.7% in sp. Carbohydrates ( = 3) were the major constituent of most seaweeds (31-34%), except in sp., with higher content in proteins than carbohydrates. Regarding the fatty acid content ( = 4), in general, saturated fatty acids (SFAs) were the most abundant followed by polyunsaturated fatty acids (PUFAs) and monounsaturated fatty acids (MUFAs). Among macro and trace elements ( = 3), shows the highest average content in Zn (71.1 mg ⋅ kg - 1 D.W.), the highest average content in K (124.8 g ⋅ kg - 1 D.W.), sp. the highest average content in P (2.1 g ⋅ kg - 1 D.W.), and sp. the highest average content of Ca (5.5 g ⋅ kg - 1 D.W.), Mg (55.8 g ⋅ kg - 1 D.W.), and Fe (336.3 mg ⋅ kg - 1 D.W.). In general, Na and K were the most abundant elements among analysed seaweed. Additionally, the microbiological results ( = 4) comply with the Portuguese guidelines (subgroup 2D) on the application of general principles of food hygiene in ready-to-eat foods.

Conclusions: Overall, the results highlight the potential of using these seaweeds as an alternative and sustainable source of elements and bioactive compounds to produce enriched food products with a beneficial potential for human nutrition.