View source for Alginic acid



==Overview==
{{Chembox new
|ImageFile=Giantkelp2 300.jpg
|ImageSize=250px
|IUPACName=magnesium; sodium; aluminum(+3) cation; hydroxyformate; oxygen(-2) anion; silicon; trihydroxide
|OtherNames=Alginic acid
|Section1= {{Chembox Identifiers
|  CASNo=
|  PubChem=6336690 
|  SMILES=C(=O)(O)[O-].[OH-].[OH-].[OH-].[O-2].[Na+].[Mg+2].[Al+3].[Si]
  }}
|Section2= {{Chembox Properties
|  Formula=CH<sub>4</sub>AlMgNaO<sub>7</sub>Si
|  MolarMass=230.4
|  Appearance=
|  Density=
|  MeltingPt=
|  BoilingPt=
|  Solubility=
  }}
|Section3= {{Chembox Hazards
|  MainHazards=
|  FlashPt=
|  Autoignition=
  }}
}}
{{SI}}
'''Alginic acid''' ('''algine''', '''alginate''') is a viscous [[natural gum|gum]] that is abundant in the cell walls of [[brown algae]].  

==Structure==

Chemically, it is a linear [[copolymer]] with [[homopolymer]]ic blocks of (1-4)-linked ß-D-mannuronate (M) and its C-5 epimer α-L-guluronate (G) residues, respectively, covalently linked together in different sequences or blocks.

The monomers can appear in homopolymeric blocks of consecutive G-residues (G-blocks), consecutive M-residues (M-blocks), alternating M and G-residues (MG-blocks) or randomly organized blocks.

==Forms==
Commercial varieties of alginate are extracted from [[seaweed]], including the giant kelp ''Macrocystis pyrifera'', ''Ascophyllum nodosum'' and various types of ''Laminaria''.  

Alginate absorbs water quickly, which makes it useful as an additive in dehydrated products such as [[diet aid|slimming aids]], and in the manufacture of [[paper]] and [[textile]]s.  It is also used for [[waterproofing]] and [[fireproofing]] fabrics, as a [[gelling agent]], for [[thickening]] drinks, [[ice cream]] and [[cosmetics]], and as a [[detoxification|detox]]ifier that can absorb poisonous metals from the blood. Alginate is also produced by certain [[bacteria]], notably [[Azotobacter]] species.  

Alginate ranges from white to yellowish brown, and takes filamentous, grainy, granular, and powdered forms. It is insoluble in [[water]] and [[organic solvent]]s, and dissolves slowly in [[base (chemistry)|basic]] solutions of [[sodium carbonate]], [[sodium hydroxide]] and [[trisodium phosphate]].

==Uses==
Alginate is used in various pharmaceuticals preparations such as [[Gaviscon]]®, Bisodol®, Asilone®. Alginate is used extensively as a mold-making material in dentistry, prosthetics, [[lifecasting]], and in [[textile]]s. It is also used in the [[food industry]], for thickening [[soup]]s and [[Fruit preserves|jellies]]. Calcium alginate is used in different types of medical products, including [[burn (injury)|burn]] dressings that promote healing and which can be removed with less pain than conventional dressings.

Also, due to alginate's biocompatibility and simple gelation with divalent cations such as Ca 2+, it is widely used for cell immobilization and encapsulation.

Alginic acid (alginato) is also used in culinary arts, most notably in the "Esferificación" (Sphereification) techniques of [[Ferrán Adriá]] of [[Barcelona]]'s [[El Bulli]], in which natural juices of fruits and vegetables are encapsulated in bubbles that "explode" on the tongue when consumed.

==See also==
* [[Sodium alginate]]
* [[Ascophyllum nodosum]]

==External links==
*[http://www.cybercolloids.net/library/alghistory/seaweeds.php Alginate seaweed sources]
*[http://www.cybercolloids.net/library/alginate/properties.php Alginate properties]



[[Category:Polysaccharides]]
[[Category:Gums]]
[[Category:Edible thickening agents]]
[[Category:Copolymers]]
[[Category:Dental materials]]

[[de:Algin]]
[[ja:アルギン酸]]
[[pt:Algina]]
[[ru:Альгиновая кислота]]
[[fi:Algiinihappo]]

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