Alginic acid

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Alginic acid
CAS number 9005-32-7 YesY
EC number 232-680-1
ATC code A02BX13
Molecular formula (C6H8O6)n
Molar mass 10,000 - 600,000
Appearance white to yellow, fibrous powder
Density 1.601 g/cm3
Acidity (pKa) 1.5-3.5
Infobox references
Macrocystis pyrifera, the largest species of giant kelp

Alginic acid, also called algin or alginate, is an anionic polysaccharide distributed widely in the cell walls of brown algae, where through binding with water it forms a viscous gum. In extracted form it absorbs water quickly; it is capable of absorbing 200-300 times its own weight in water.[1] Its colour ranges from white to yellowish-brown. It is sold in filamentous, granular or powdered forms.






Alginates from different species of brown seaweed often have variations in their chemical structure, resulting in different physical properties. For example, some may yield an alginate that gives a strong gel, another a weaker gel; one may readily give a cream/white alginate, another may give that only with difficulty and is best used for technical applications where color does not matter.[2]








Alginate absorbs water quickly, which makes it useful as an additive in dehydrated products such as slimming aids, and in the manufacture of paper and textiles. It is also used for waterproofing and fireproofing fabrics, as a gelling agent, and for thickening drinks, ice cream and cosmetics.

Alginate is used in various pharmaceutical preparations such as Gaviscon, Bisodol, and Asilone. Alginate is used extensively as an impression-making material in dentistry, prosthetics, lifecasting and occasionally for creating positives for small-scale casting. It is also used in the food industry, for thickening soups and jellies.

Calcium alginate is used in different types of medical products, including burn dressings that promote healing and can be removed with less pain than conventional dressings.

Also, due to alginate's biocompatibility and simple gelation with divalent cations such as Ca2+, it is widely used for cell immobilization and encapsulation.

Alginic acid (alginato) is also used in culinary arts, most notably in the Spherification techniques of Ferran Adrià.[5]

Due to its ability to absorb water quickly, alginate can be changed through a lyophilization process to a new structure that has the ability to expand. It is used in the weight loss industry as an appetite suppressant.

In March, 2010 researchers at Newcastle University announced that dietary alginates can reduce human fat uptake by more than 75%.[6]

Sodium alginate[edit]

As a flavorless gum, it is used by the foods industry to increase viscosity and as an emulsifier. It is also used in indigestion tablets and the preparation of dental impressions.

A major application for sodium alginate is in reactive dye printing, as thickener for reactive dyestuffs (such as the Procion cotton-reactive dyes) in textile screen-printing and carpet jet-printing. Alginates do not react with these dyes and wash out easily, unlike starch-based thickeners.

Sodium alginate is a good chelator for pulling radioactive substances from the body, such as iodine-131 and strontium-90, that have taken the place of their non-radioactive counterparts.[7][8] It is also used in immobilizing enzymes by inclusion.


Nowadays, it is also used in the biological experiments for the immobilization of cells to obtain important products like alcohols, organic acids, etc.

In recent years, sodium alginate has been used in molecular gastronomy. Ferran Adrià pioneered the technique, and it has since been used by chefs such as Grant Achatz and Heston Blumenthal. Sodium alginate is combined with calcium lactate or similar compounds to create spheres of liquid surrounded by a thin jelly membrane.

Potassium alginate[edit]

Potassium alginate is widely used in foods as a stabilizer, thickener, and emulsifier.

Its use as a pharmaceutical excipient is currently limited to experimental hydrogel systems. The viscosity, adhesiveness, elasticity, stiffness, and cohesiveness of potassium alginate hydrogels have been determined and compared with values from a range of other hydrogel-forming materials. The effect of calcium ions on the rheological properties of procyanidin hydrogels containing potassium alginate and intended for oral administration has also been investigated.

See also[edit]


  1. ^ Raymond C. Rowe, Paul J. Sheskey, Marian E. Quinn, ed. (2009), "Adipic Acid", Handbook of Pharmaceutical Excipients (Rowe, Handbook of Pharmaceutical Excipients) (Sixth ed.), Pharmaceutical Pr, pp. 11–12, ISBN 0-85369-792-2 
  2. ^ FAO FISHERIES TECHNICAL PAPER 441, Dennis J. McHugh, School of Chemistry, University College, University of New South Wales and Australian Defence Force Academy Canberra Australia
  4. ^ FAO Fisheries Technical Paper, 2003
  5. ^ "Lo Mejor de la Gastronomia". Archived from the original on 1 December 2007. Retrieved 2007-11-14. 
  6. ^ "Seaweed to tackle rising tide of obesity". Newcastle University. Archived from the original on 25 March 2010. Retrieved 2010-03-22. 
  7. ^ Sutton, A., Harrison, G. E., Carr, T. E., and Barltrop, D. Reduction in the absorption of dietary strontium in children by an alginate derivative. Br.J.Radiol. 44[523], 567. 1971
  8. ^ Sutton, A., Harrison, B. E., Carr, T. E., and Barltrop, D. Reduction in the absorption of dietary strontium in children by an alginate derivative. Int.J.Radiat.Biol.Relat Stud.Phys.Chem.Med. 19[1], 79-85. 1971

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