Alginic acid, also called algin or alginate, is an anionic polysaccharide

Polysaccharide

Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

 distributed widely in the cell wall

Cell wall

The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...

s of brown algae

Brown algae

The Phaeophyceae or brown algae , is a large group of mostly marine multicellular algae, including many seaweeds of colder Northern Hemisphere waters. They play an important role in marine environments, both as food and for the habitats they form...

, where it, through binding water, forms a viscous gum

Natural gum

Natural gums are polysaccharides of natural origin, capable of causing a large viscosity increase in solution, even at small concentrations. In the food industry they are used as thickening agents, gelling agents, emulsifying agents, and stabilizers...

. In extracted form it absorbs water quickly; it is capable of absorbing 200-300 times its own weight in water. Its colour ranges from white to yellowish-brown. It is sold in filamentous, granular or powdered forms.

Structure

It is a linear copolymer with homopolymeric blocks of (1-4)-linked β-D-mannuronate (M) and its C-5 epimer

Epimer

In chemistry, epimers are diastereomers that differ in configuration of only one stereogenic center. Diastereomers are a class of stereoisomers that are non-superposable, non-mirror images of one another....

 α-L-guluronate (G) residues, respectively, covalently linked together in different sequences or blocks.

The monomer

Monomer

A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...

s can appear in homopolymeric blocks of consecutive G-residues (G-blocks), consecutive M-residues (M-blocks) or alternating M and G-residues (MG-blocks).

Forms

Commercial varieties of alginate are extracted from seaweed

Seaweed

Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...

, including the giant kelp

Kelp

Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....

 Macrocystis pyrifera

Macrocystis pyrifera

Macrocystis pyrifera, commonly known as Giant kelp or Giant bladder kelp, is a species of kelp , and one of four species in the genus Macrocystis...

, Ascophyllum nodosum

Ascophyllum nodosum

Ascophyllum nodosum is a large, common brown alga in the family Fucaceae, being the only species in the genus Ascophyllum. It is seaweed of the northern Atlantic Ocean, also known as rockweed, Norwegian kelp, knotted kelp, knotted wrack or egg wrack...

, and various types of Laminaria

Laminaria

Laminaria is a genus of 31 species of brown algae , all sharing the common name "kelp". This economically important genus is characterized by long, leathery laminae and relatively large size. Some species are referred to by the common name Devil's apron, due to their shape, or sea colander, due to...

. It is also produced by two bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

l genera

Genera

Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...

 Pseudomonas

Pseudomonas

Pseudomonas is a genus of gammaproteobacteria, belonging to the family Pseudomonadaceae containing 191 validly described species.Recently, 16S rRNA sequence analysis has redefined the taxonomy of many bacterial species. As a result, the genus Pseudomonas includes strains formerly classified in the...

and Azotobacter

Azotobacter

Azotobacter is a genus of usually motile, oval or spherical bacteria that form thick-walled cysts and may produce large quantities of capsular slime. They are aerobic, free-living soil microbes which play an important role in the nitrogen cycle in nature, binding atmospheric nitrogen, which is...

, which played a major role in the unravelling of its biosynthesis

Biosynthesis

Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...

 pathway. Bacterial alginates are useful for the production of micro- or nanostructures suitable for medical applications.

Uses

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

Waterproofing

Waterproof or water-resistant describes objects relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environments or under water to specified depths...

 and fireproofing

Fireproofing

Fireproofing, a passive fire protection measure, refers to the act of making materials or structures more resistant to fire, or to those materials themselves, or the act of applying such materials. Applying a certification listed fireproofing system to certain structures allows these to have a...

 fabrics, as a gelling agent, and for thickening

Thickening

In cooking, thickening is the process of increasing the viscosity of a liquid either by reduction, or by the addition of a thickening agent, typically containing starch....

 drinks, ice cream and cosmetics.

Alginate is used in various pharmaceutical preparations such as Gaviscon

Gaviscon

Gaviscon is a non-prescription medication for the treatment of heartburn and GERD. It is produced and distributed in the UK by Reckitt Benckiser and by GlaxoSmithKline in the US and Canada.Gaviscon is taken to treat heartburn, similarly to other antacids...

, Bisodol, and Asilone. Alginate is used extensively as an impression

Impression (dental)

A dental impression is an imprint of hard and/or suft tissues, formed with specific types of impression materials that is used in different area of dentistry including prosthetics , restorative, diagnosis and Oral and Maxillofacial surgery for both intra oral and or extra oral aims.The required...

-making material in dentistry

Dentistry

Dentistry is the branch of medicine that is involved in the study, diagnosis, prevention, and treatment of diseases, disorders and conditions of the oral cavity, maxillofacial area and the adjacent and associated structures and their impact on the human body. Dentistry is widely considered...

, prosthetics, lifecasting

Lifecasting

Lifecasting is the process of creating a three-dimensional copy of a living human body, through the use of molding and casting techniques. In rare cases lifecasting is also practiced on living animals....

 and occasionally for creating positives for small-scale casting

Casting

In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...

. 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

Biocompatibility

Biocompatibility is related to the behavior of biomaterials in various contexts. The term may refer to specific properties of a material without specifying where or how the material is used , or to more empirical clinical success of a whole device in...

 and simple gelation with divalent

Divalent

In chemistry, a divalent ion or molecule has a valence of two and thus can form two bonds with other ions or molecules. An older term for divalent is bivalent....

 cations such as Ca²⁺, it is widely used for cell immobilization

Immobilized whole cell

The immobilized whole cell system is an alternative to enzyme immobilization. Unlike enzyme immobilization, where the enzyme is attached to a substrate , in immobilized whole cell systems, the target cell is immobilized. Such methods may be implemented when the enzymes required are difficult or...

 and encapsulation

Immobilized enzyme

An immobilized enzyme is an enzyme that is attached to an inert, insoluble material such as calcium alginate . This can provide increased resistance to changes in conditions such as pH or temperature...

.

Alginic acid (alginato) is also used in culinary art

Culinary art

Culinary art is the art of preparing and cooking foods. The word "culinary" is defined as something related to, or connected with, cooking. A culinarion is a person working in the culinary arts. A culinarian working in restaurants is commonly known as a cook or a chef. Culinary artists are...

s, most notably in the "Esferificación" (Sphereification

Spherification

Spherification is the culinary process of shaping a liquid into spheres which visually and texturally resemble caviar. The technique was originally discovered by Unilever in the 1950s Spherification is the culinary process of shaping a liquid into spheres which visually and texturally resemble...

) techniques of Ferran Adrià

Ferran Adrià

Ferran Adrià i Acosta is a Catalan chef born on May 14, 1962 in L'Hospitalet de Llobregat. He was the head chef of the El Bulli restaurant in Roses on the Costa Brava, and is considered one of the best chefs in the world.-Career:...

 of El Bulli

El Bulli

elBulli was a Michelin 3-star restaurant near the town of Roses, Catalonia, Spain, run by chef Ferran Adrià. The small restaurant overlooked Cala Montjoi, a bay on Catalonia's Costa Brava, and has been described as "the most imaginative generator of haute cuisine on the planet" and does a great...

 in Roses, Girona, where natural juices of fruits and vegetables are encapsulated in bubbles that "explode" on the tongue when consumed. One of the most famous examples of this use of alginic acid was when Ferran Adrià

Ferran Adrià

Ferran Adrià i Acosta is a Catalan chef born on May 14, 1962 in L'Hospitalet de Llobregat. He was the head chef of the El Bulli restaurant in Roses on the Costa Brava, and is considered one of the best chefs in the world.-Career:...

 used alginic acid to make apple caviar.

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%.

Sodium alginate

The chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 sodium alginate is the sodium

Sodium

Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 salt of alginic acid. Its empirical formula

Empirical formula

In chemistry, the empirical formula of a chemical compound is the simplest positive integer ratio of atoms of each element present in a compound. An empirical formula makes no reference to isomerism, structure, or absolute number of atoms. The empirical formula is used as standard for most ionic...

 is NaC₆H₇O₆. Sodium alginate is a gum

Natural gum

Natural gums are polysaccharides of natural origin, capable of causing a large viscosity increase in solution, even at small concentrations. In the food industry they are used as thickening agents, gelling agents, emulsifying agents, and stabilizers...

, extracted from the cell walls of brown algae

Brown algae

The Phaeophyceae or brown algae , is a large group of mostly marine multicellular algae, including many seaweeds of colder Northern Hemisphere waters. They play an important role in marine environments, both as food and for the habitats they form...

.

Uses

Its form as a flavorless gum

Natural gum

Natural gums are polysaccharides of natural origin, capable of causing a large viscosity increase in solution, even at small concentrations. In the food industry they are used as thickening agents, gelling agents, emulsifying agents, and stabilizers...

, is used by the foods industry to increase viscosity

Viscosity

Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher 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

Reactive dye printing

Reactive dye printing is a method of printing a dye or wax by using mixes thereof to create colors. With a binder and a heat-activated printing additive, images can be permanently bonded to the substrate . These reactions are generally heat-activated.-External links:* 6,840,614...

, as thickener for reactive dye

Reactive dye

In a reactive dye a chromophore contains a substituent that is activated and allowed to directly react to the surface of the substrate. Reactive dyes have good fastness properties owing to the bonding that occurs during dyeing....

stuffs (such as the Procion cotton-reactive dyes) in textile screen-printing

Textile printing

Textile printing is the process of applying colour to fabric in definite patterns or designs. In properly printed fabrics the colour is bonded with the fiber, so as to resist washing and friction...

 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 toxins from the body, such as iodine-131 and strontium-90 that have taken the place of their non-radioactive counterparts. It is also used in immobilizing enzymes

Immobilized enzyme

An immobilized enzyme is an enzyme that is attached to an inert, insoluble material such as calcium alginate . This can provide increased resistance to changes in conditions such as pH or temperature...

 by inclusion.

As a food additive, sodium alginate is used especially in the production of gel-like foods. For example, bakers' "Chellies" are often gelled alginate "jam." Also, the pimento stuffing in prepared cocktail olives is usually injected as a slurry at the same time that the stone is ejected; the slurry is subsequently set by immersing the olive in a solution of a calcium salt, which causes rapid gelation by electrostatic cross-linking. A similar process can be used to make "chunks" of everything from cat food through "reformed" ham or fish to "fruit" pieces for pies. It has the E-number 401.

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

Molecular gastronomy

Molecular gastronomy is a subdiscipline of food science that seeks to investigate, explain and make practical use of the physical and chemical transformations of ingredients that occur while cooking, as well as the social, artistic and technical components of culinary and gastronomic phenomena in...

 at some of the best restaurants in the world. Ferran Adria

Ferran Adrià

Ferran Adrià i Acosta is a Catalan chef born on May 14, 1962 in L'Hospitalet de Llobregat. He was the head chef of the El Bulli restaurant in Roses on the Costa Brava, and is considered one of the best chefs in the world.-Career:...

 pioneered the technique, and it has since been used by chefs such as Grant Achatz

Grant Achatz

Grant Achatz is an American chef and restaurateur often identified as one of the leaders in molecular gastronomy or progressive cuisine...

 and Heston Blumenthal

Heston Blumenthal

Heston Marc Blumenthal OBE is an English chef and owner of The Fat Duck, a three-Michelin-starred restaurant in Bray, Berkshire voted Best Restaurant in the UK by The Good Food Guide 2007 and 2009, and voted best restaurant in the world by Restaurant magazine in 2005...

. Sodium alginate is combined with calcium lactate or similar compound to create spheres of liquid surrounded by a thin jelly membrane.

It has been used as a filler for artificial eggs. Kits sold in China advertise that by pouring a filler composed primarily of sodium alginate into a shell of calcium carbonate, a fake egg can be manufactured for one-quarter the price of a real one.

Potassium alginate

Potassium alginate is a chemical compound that is the potassium salt

Salt

In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

 of alginic acid. It is an extract of seaweed. Its empirical chemical formula is KC₆H₇O₆.

Uses

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

Viscosity

Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

, adhesiveness, elasticity

Elasticity (physics)

In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform or distort is removed. The relative amount of deformation is called the strain....

, 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.

External links

• Alginate seaweed sources
• Alginate properties
• article Wired
  Wired (magazine)
  Wired is a full-color monthly American magazine and on-line periodical, published since January 1993, that reports on how new and developing technology affects culture, the economy, and politics...
  
   on Easy Cheese
  Easy Cheese
  Easy Cheese is the trademark for a processed cheese product distributed by Kraft Foods, also referred to as aerosol cheese or spray cheese, and is a descendant of squeeze cheese . It comes packaged in a spray can, much like canned whipped cream and does not require refrigeration...
  
  , describing sodium alginate