Chemical Composition of Seaweeds

The table below gives the chemical composition of selected, representative seaweeds, some of which are currently used for food or have been used as food in the past. All figures, except for water (as percentage), are given as grams per 100 grams of dry matter. When no data are available "nd" is inserted.

In regard to the amount of protein, the convention is to convert the total nitrogen to protein by multiplying by 6.25. This should be treated with some caution as, for example, the amount of free nitrate will affect the total nirtogen level. Free nitrates are found in varying amounts in red and brown algae.

Fact sheets for Irish macroalgae

Edwards, M., Hanniffy, D., Heesch, S., Hernández-Kantún, J., Moniz, M., Queguineur, B., Ratcliff, J., Soler-Vila, A., & Wan, A. (2012). Macroalgae Fact-sheets. Edited by Soler-Vila, A., & Moniz, M. 40 pp. Download.

These figures were taken, with slight modification, from Indergaard & Minsaas (1991). Further references are given below the table.

Ascophyllum
nodosum

Laminaria digitata

Alaria esculenta

Palmaria palmata

Porphyra yezoensis

Ulva
species

Type Brown Brown Brown Red Red Green
Water (%) 70-85 73-90 73-86 79-88 nd 78
Ash 15-25 73-90 73-86 15-30 7.8 13-22
Total carbohydrates - - - - 44.4 42-46
Alginic acid 15-30 20-45 21-42 0 0 0
Xylans 0 0 0 29-45 0 0
Laminaran 0-10 0-18 0-34 0 0 0
Mannitol 5-10 4-16 4-13 0 0 0
Fucoidan 4-10 2-4 nd 0 0 0
Floridoside 0 0 0 2-20 nd 0
Other carbohydrates c. 10 1-2 1-2 nd nd nd
Protein 5-10 8-15 9-18 8-25 43.6 15-25
Fat 2-7 1-2 1-2 0.3-0.8 2.1 0.6-0.7
Tannins 2-10 c. 1 0.5-6.0 nd nd nd
Potassium 2-3 1.3-3.8 nd 7-9 2.4 o.7
Sodium 3-4 0.9-2.2 nd 2.0-2.5 0.6 3.3
Magnesium 0.5-0.9 0.5-0.8 nd 0.4-0.5 nd nd
Iodine 0.01-0.1 0.3-1.1 0.05 0.01-0.1 nd nd
References
(given below)
Baardseth (1970) Haug & Jensen (1954);
Gayral & Cosson (1973);
Jensen (1956a, 1956b)
Haug & Jensen (1954); Baardseth & Haug (1953); Jensen (1956a, 1956b) Morgan et al., (1980) Nisizawa et al., (1987);

Arasaki & Arasaki (1983);

Nisizawa et al., (1987); Levring et al. (1969)

References

Arasaki, S. & Arasaki, T. 1983. Vegetables from the Sea. Japan Publ. Inc., Tokyo,

Baardseth, E. 1970. Synopsis of biological data on knobbed wrack Ascophyllum nodosum (Linnaeus) Le Jolis. FAO Fisheries Synopsis 38:1-38.

Gayral, P. & Cosson, J. 1973. Exposé synoptique des données biologiques sur la laminaire digitée Laminaria digitata. Fisheries Synopsis FAO 89(v + 45):

Haug, A. & Jensen , A. 1954. Seasonal Variations on the Checmical Copmosition of Alaria esculenta, Laminaria saccharina, Laminaria hyperborea and Laminaria digitata from Northern Norway. Reports of the Norwegian Institute of Seaweed Research No. 4.

Indergaard, M. & Minsaas, J. 1991. Animal and human nutrition. In Guiry, M. D. & Blunden, G. (Ed.) Seaweed Resources in Europe: Uses and Potential. John Wiley & Sons, Chichester, 21-64.

Jensen, A. 1956. Component sugars of some common brown algae. Rep. Norw. Inst. Seaweed Res. No. 9.

Jensen, A. 1956. Preliminary investigations of the carbohydrates of Laminaria digitata and Fucus serratus. Rep. Norw. Inst. Seaweed Res. No. 10.

Morgan, K.C.,Wright, J.L.C. & Simpson, F.J. 1980. Review of chemical constituents of the red alga Palmaria palmata (dulse). Econ. Bot. 34:27-50.

Nisizawa, K.,Noda, H.,Kikuchi, R. & Watanabe, T. 1987. The main seaweed foods in Japan. Proc. Intl. Seaweed Symp. 12:5-29.