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

Abstract

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 (Chondrus crispus, Palmaria palmata, Porphyra sp., and Ulva 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 (n = 3) were very low (1.6–2.3%), particularly in Palmaria palmata, and Chondrus crispus (1.6–1.7%). The protein content (n = 4) varied from 14.4% in P. palmata to 23.7% in Porphyra sp. Carbohydrates (n = 3) were the major constituent of most seaweeds (31–34%), except in Porphyra sp., with higher content in proteins than carbohydrates. Regarding the fatty acid content (n = 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 (n = 3), Chondrus crispus shows the highest average content in Zn (71.1 mg ⋅ kg - 1 D.W.), Palmaria palmata the highest average content in K (124.8 g ⋅ kg - 1 D.W.), Porphyra sp. the highest average content in P (2.1 g ⋅ kg - 1 D.W.), and Ulva 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 (n = 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.

Keywords

• edible seaweed species
• proximal composition
• chemical analysis
• microbial load