Nutritional Composition of the Atlantic Seaweeds Ulva rigida, Codium tomentosum, Palmaria palmata and Porphyra purpurea

Macroalgae are regarded as a healthy food due to their composition and nutritional properties. In this work, nutritional composition of two green (Ulva rigida, Codium tomentosum) and two red (Palmaria palmata, Porphyra purpurea) edible seaweed was studied. Total lipids were measured gravimetrically as evaporated mass after petroleum-ether Soxhlet extraction of samples. In addition, fatty acid profile was determined by gas chromatography coupled to a flame ionization detector (GC-FID). Results showed that all studied species were accounted for very low levels of lipids (<1% dw), but levels of unsaturated fatty acids oleic, linoleic, and linolenic acids were present at high concentrations, with P. palmata displaying the highest quantities (>200 mg C18:1/g extract). In parallel, proteins were quantified following the macro-Kjeldahl method. In this analysis, red algae, especially P. purpurea, showed significant protein content up to 30% DW. Total organic acids were found by ultra-filtration liquid-chromatography coupled to an amperometry detector (UFLC-PAD) after an acid extraction, P. purpurea being the algae with the higher organic acid content (10.61% dw). Minerals were identified and quantified by inductively coupled plasma atomic emission spectroscopy (ICP-OES), suggesting that both algae groups are rich in K and Mg (>15 g/kg), but U. rigida also displayed a remarkable iron content (>1 g Fe/kg). Other detected minerals in minor concentrations were Ca, P or F. Altogether, results corroborate that these edible algae are a good source of nutrients in accordance with literature.