Molecular Formula: C12H20O12P2
CAS Number: 9005-32-7
EC Number: 232-680-1
E number: E400
MDL number: MFCD00081310
Alginic acid, also referred to as algin or alginate, is a hydrophilic or anionic polysaccharide isolated from certain brown seaweed (Phacophycae) via alkaline extraction.
Alginic acid is present in cell walls of brown algae where Alginate forms a viscous gel when binding with water.
Alginic acid is a linear polymer consisted of L-glucuronic acid and D-mannuronic acid residues connected via 1,4-glycosidic linkages.
Available in different types of salt, alginic acid has been used in a variety of uses in food, cosmetics and pharmaceu-tical products for over 100 years.
Alginic acid is an FDA-approved food ingredient in soup and soup mixes as an emulsifier, thickener, and stabilizer.
Alginic acid is also available in oral dietary supplements and is found in antacids such as Gaviscon to inhibit gastroesophageal reflux by creating a physical barrier in presence of gastric acid.
Alginate-based raft-forming formulations in the management of heartburn and gastric acid reflux have been used worldwide for over 30 years.
Alginic acid reacts with the gastric acid to form a viscous gel or “raft” that floats on the surface of stomach contents.
This activity acts as a mechanical barrier to reduce reflux or protect the oesophageal mucosa during reflux.
Usually combined antacids such as Ca carbonate, Mg carbonate, and Al hydroxide works synergistically with alginic acid by neutralising the excess acid in the stomach.
Alginic acid is a high molecular weight linear polymer isolated from seaweed.
Alginic acid is a linear β-1→4-linked polymer of n-mannuronic and L-guluronic acid.
Alginic acid is an acid polysaccharide present in the extracellular matrix of brown algae.
Alginic acid is reported to inhibit the reverse transcriptase activity of HIV.
Structural investigation of alginic acid, a marine algal polysaccharide poly-α-L-guluronic acid, has been reported.
Anti-inflammatory effect of alginic acid, isolated from the brown algae Sargassum wightii, in type II collagen induced arthritic rats has been reported.
Pyrolysis of alginic acid using py-GC/MS over a wide temperature range (200-800°C) and thermogravimetric analysis (TGA) has been reported.
Alginic acid was reported to cause the biocorrosion of thin films of copper on germanium internal reflection elements (IREs).
Alginic acid is a biopolymer formed from chains of polyuronic acids and is extracted from algae sources, mainly Laminaria; Alginate has a wide range of biological applications and may in the future be used in controlled-release products.
At present, Alginate is approved for use only in combination with antacids. Alginic acid can absorb 200-300 times Alginic acids weight in water and solutes at low pH yielding a high viscosity, high pH gel.
This forms a physical barrier floating in the gastric acid contents, reducing acid reflux into the esophagus.
Alginic acid is useful for treating gastroesophageal reflux disease and indigestion.
Alginic acid, also called algin, is a naturally occurring, edible polysaccharide found in brown algae.
Alginate is hydrophilic and forms a viscous gum when hydrated.
With metals such as sodium and calcium, its salts are known as alginates.
Alginates colour ranges from white to yellowish-brown.
Alginate is sold in filamentous, granular, or powdered forms.
Alginic acid, also called algin or alginate, is an anionic polysaccharide distributed widely in the cell walls of brown algae, including Laminaria and Ascophyllum species.
Alginate is formed by linear block copolymerization of d-mannuronic acid and l-guluronic acid.
Alginates are linear unbranched polysaccharides which contain different amounts of (1→4′)-linked β-d-mannuronic acid and α-l-guluronic acid residues.
Alginate is biodegradable, has controllable porosity, and may be linked to other biologically active molecules.
Interestingly, encapsulation of certain cell types into alginate beads may actually enhance cell survival and growth.
Due to their hemostatic properties, alginate and its salts are used for wound treatment in various forms such as gel or sponge.
Calcium alginate can also increase cellular activity properties such as adhesion and proliferation (Thomas, 2000a,b,c).
Obtained from processed algae, calcium alginate, calcium–sodium alginate, collagen–alginate, and gelatin–alginate are highly absorbent natural fiber dressings (Qin et al., 2006; Thu et al., 2012).
Alginate can absorb water and body fluids up to 20 times Alginates weight, resulting in a hydrophilic gel.
The formed gel is weak, but Alginate maintains a moist wound healing environment.
Alginic acid is a naturally occurring hydrophilic colloidal polysaccharide obtained from the various species of brown seaweed (Phaeophyceae).
Alginate is a linear copolymer consisting mainly of residues of ß-1,4-linked Dmannuronic acid and a-1,4-linked L-glucuronic acid.
These monomers are often arranged in homopolymeric blocks separated by regions approximating an alternating sequence of the two acid monomers.
Alginic acid is a linear copolymer with homopolymeric blocks of (1-4)-linked ?-D-mannuronate (M) and its C-5 epimer ?-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.
Molecular weight varies from 10,000 to 600,000.
Analysis is a challenging task due to a wide distribution of molecular weights.
Alginic acid analyzed in ion-exclusion and size exclusion mode on Primesep C mixed-mode cation exchange column.
Alginic acid elutes before void as a single peak with good symmetry.
Method can be used for quantitation of alginic acid in various formulation.
Low UV or ELSD can be employed.
Alginate" is the term usually used for the salts of alginic acid, but Alginate can also refer to all the derivatives of alginic acid and alginic acid itself; in some publications the term "algin" is used instead of alginate.
Alginate is present in the cell walls of brown algae as the calcium, magnesium and sodium salts of alginic acid.
The goal of the extraction process is to obtain dry, powdered, sodium alginate.
The calcium and magnesium salts do not dissolve in water; the sodium salt does.
The rationale behind the extraction of alginate from the seaweed is to convert all the alginate salts to the sodium salt, dissolve this in water, and remove the seaweed residue by filtration.
The alginate must then be recovered from the aqueous solution.
The solution is very dilute and evaporation of the water is not economic.
There are two different ways of recovering the alginate.
The first is to add acid, which causes alginic acid to form; this does not dissolve in water and the solid alginic acid is separated from the water.
The alginic acid separates as a soft gel and some of the water must be removed from this.
After this has been done, alcohol is added to the alginic acid, followed by sodium carbonate which converts the alginic acid into sodium alginate.
The sodium alginate does not dissolve in the mixture of alcohol and water, so Alginate can be separated from the mixture, dried and milled to an appropriate particle size that depends on its particular application.
The second way of recovering the sodium alginate from the initial extraction solution is to add a calcium salt.
This causes calcium alginate to form with a fibrous texture; Alginate does not dissolve in water and can be separated from it.
The separated calcium alginate is suspended in water and acid is added to convert it into alginic acid.
This fibrous alginic acid is easily separated, placed in a planetary type mixer with alcohol, and sodium carbonate is gradually added to the paste until all the alginic acid is converted to sodium alginate.
The paste of sodium alginate is sometimes extruded into pellets that are then dried and milled.
The process appears to be straightforward, certainly the chemistry is simple:
Convert the insoluble alginate salts in the seaweed into soluble sodium alginate; precipitate either alginic acid or calcium alginate from the extract solution of sodium alginate; convert either of these back to sodium alginate, this time in a mixture of alcohol and water, in which the sodium salt does not dissolve.
The difficulties lie in handling the materials encountered in the process, and to understand these problems a little more detail of the process is required.
To extract the alginate, the seaweed is broken into pieces and stirred with a hot solution of an alkali, usually sodium carbonate.
Over a period of about two hours, the alginate dissolves as sodium alginate to give a very thick slurry.
This slurry also contains the part of the seaweed that does not dissolve, mainly cellulose.
This insoluble residue must be removed from the solution.
The solution is too thick (viscous) to be filtered and must be diluted with a very large quantity of water.
After dilution, the solution is forced through a filter cloth in a filter press.
However, the pieces of undissolved residue are very fine and can quickly clog the filter cloth.
Therefore, before filtration is started, a filter aid, such as diatomaceous earth, must be added; this holds most of the fine particles away from the surface of the filter cloth and facilitates filtration.
However, filter aid is expensive and can make a significant contribution to costs.
To reduce the quantity of filter aid needed, some processors force air into the extract as Alginate is being diluted with water (the extract and diluting water are mixed in an in-line mixer into which air is forced).
Fine air bubbles attach themselves to the particles of residue.
The diluted extract is left standing for several hours while the air rises to the top, taking the residue particles with it.
This frothy mix of air and residue is removed from the top and the solution is withdrawn from the bottom and pumped to the filter.
The next step is precipitation of the alginate from the filtered solution, either as alginic acid or calcium alginate.
Since the mid-1970s, different forms of alginates such as alginate salt, alginic acids and propylene glycol alginates have been used successfully in pharmaceutical applications.
Alginates are extensively used in pharmaceutical applications due to their unique properties.
Some of the applications wherein alginates are used include film formers, disintegrants, for controlled release and control of gastric reflux as well as thickening and stabilization.
These are but a few of the pharmaceutical applications in which alginate have been used.
One of the advantages of alginate is that it hydrates quickly whether in cold or hot water.
Alginates are also known to form gels that are thermally irreversible as well as clear, uniform and glossy films.
In addition, when alginates are mixed along with water, Alginate easily changes to alginic acid in a below 4 PH.
Some of the other uses of alginates in the pharmaceutical field include
Alginic acid is one of the main carbohydrates of the Phaeophycae, the brown seaweeds, its function not being clear.
The proportion varies with the season, species of Laminaria containing 24% of alginic acid in February and only 14% in September.
To isolate it1the cleaned weed is first steeped in dilute acid, washed and then extracted with sodium carbonate solution, when a solution of sodium alginate is obtained.
This material finds many commercial uses.
Alginate finds uses in cold setting jellies, as a stabiliser in many foods, particularly ice cream, as a.thickener in textile printing, in the surface sizing of paper and in water purification.
Alginic acid is a high molecular weight polysaccharide and until 1955 Alginate was thought that it contained only residues of D-mannuronic acid.
However, Fischer and Dorfel showed that hydrolysis gave L-guluronic acid, the C-5 epimer of D-mannuronic, as well as D-mannuronic acid.
Methylation analysis indicates that both these units are 1,4- linked, a conclusion that is substantiated by the application of other methods of structural investigation, and with which results of earlier work are consistent.
Isolation of 4-0-ß-D-mannopyranosyl-D-mannopyranose from a partial hydrolysate of the reduced polysaccharide indicates that the mannuronic acid residues in alginicacid are linked through their C-4 positions by a ß-linkage and that the linkage is 1,4-pyranosyl rather than 1,5-furanosyl.
Partial fractionation into fractions rich in mannuronic and guluronic acids, respectively, has been achieved, but repeated fractionation failed to separate a polymer which contained only mannuronic or guluronic acid residues.
Proof that the two acids appear together in at least some of the alginic acid molecules was supplied by the isolation of oligouronic acids containing both acids, and of a crystalline mannosyl- gulose from partial acid hydrolysates of alginic acid and its reduction product respectively.
A study of the constitution of alginic acid by partial acid hydrolysis has been carried out by Haug, Snidsrod and Larsen.
Heterogeneous hydrolysis of the alginate was carried out with oxalic acid.
Results showed that a certain amount of the alginate passed rapidly into solution, but even prolonged hydrolysis did not increase the concentration of carbohydrate in the solution to more than corresponding to 28% of the alginate.
This clearly indicated that only part of the alginate sample was available for hydrolysis, while the rest of the sample was protected against hydrolysis or hydrolysed very slowly.
The insoluble material could only be further degraded when Alginate was washed, dissolved in dilute alkali and then retreated with oxalic acid.
Even then there was a limit to the amount of hydrolysis taking place.
The insoluble fraction could be fractionated into one fraction which contained predominantly guluronic acid residues and another which contained predominantly mannuronic acid residues.
Significantly, no fraction with an intermediate uronic acid composition could be prepared.
The number average length of the insoluble chains was 20 -30.
The soluble fraction was shown tentatively to consist predominantly of the two monomers and a diuronide containing both the monomers.
From these results HaugkandaLarsen deduced that alginic acid consists of blocks of 20 -30 monomer units with either predominantly mannuronic or guluronic acids and that these blocks are separated by regions with another sequence of uronic acid residues, probably with a large proportion of alternating mannuronic and guluronic acid residues.
The blocks with a highly regular structure more easily form crystalline regions with a 3. much lower rate of hydrolysis than the more amorphous regions.
Alginate has still to be shown conclusively whether structural irregularities, such as branching or non -1,4-linking, ever occurs in the molecule.
The incomplete oxidation of sodium alginate by periodate would be explained if such irregularities were present.
These questions are more fully examined in Section A. Another unsolved problem is the configuration of the guluronosyl linkage.
Alginate is noteworthy that a bacterial polysaccharide resembling alginic acid has been isolated from Azotobacter vinelandii and Pseudomonas aeruginosa.
STudies are not yet so complete as on algal alginic acid and there would seem to be a close structural similarity except that the bacterial polymer is at least sometimes 0- acetylated.
Degradation of alginate by a ß-elimination reaction has been achieved both enzynically and chemically (see Section C), and oxidative degradation by a free -radical mechanism by naturally - occuring phenolic compounds has also been shown to take place.
In some ways, alginic acid has a more simple structure than pectic acid, a related uronic acid polymer from higher plants, in which the monomer is galacturonic acid.
Pectin is similar to alginic acid in that it contains a backbone of uronic acid residues, but blocks of polygalacturonic acid appear to be interrupted by occasional neutral residues (rhamnose).
Neutral side chains are also present in varying degree, depending on the source of the pectin.
Unlike pectic acid, alginic ei.cid does not occur in the esterified state%nor do neutral sugars ever seem to be part of the molecule.
The chemical reactions of alginic acid are therefore of interest, not only for their own sake, but also because they might usefully be applied in the structure determination of the more complex pectic substances.
One of the aims of the work which is reported in this Thesis, has been to use alginic acid to develop new approaches to the structure determination of uronic acid- containing polysaccharides.
Details of these approaches are given in Sections B and C.
X -ray analysis of alginic acid gives well- developed diffraction patterns, but Alginate has since been shown by Frei and Preston that the sample examined was in fact a guluronic acid -rich sample.
The data obtained therefore corresponded to polyguluronic acid and not to polymannuronic acid as was originally supposed.
If we ignore the C -6 carbon atom then polyguluronic acid has the same carbon skeleton as cellulose (as well as xylan, mannan and polymannuronic acid) and these two polymers are indeed related in having a 2 -fold screw axis along the fibre axis although the fibre repeat distance is somewhat shorter for polyguluronic acid - 8.71 as opposed to 10.32 for cellulose.
Frei and Preston reached the conclusion that the algal cell wall contains mainly material rich in guluronic acid whereas the intercellular alginic acid is primarily polymannuronic acid.
The physical properties of alginate solutions are in many ways similar to those of pectins in the higher plant kingdom and to those of the sulphated polysaccharides from the red seaweeds e.g. K- carrageenan.
For example, all form strong, reversible, cation -sensitive gels.
This similarity, and the fact that all these polysaccharides occur at least partly in the intercellular parts of plant tissue, suggest that they might have similar biological functions.
Accordingly, in seeking to understand the conformation, and the physical and biological properties of alginic acids, Alginate would seem worthwhile to study all three types of polysaccharide together.
Some progress has been made in this laboratory towards the determination of the conformation of K-carrageenan by X-ray diffraction; this is described later in this Thesis (Section D) together with the results of an attempt wo develop the X-ray methods further and to apply them to alginic and pectic acids.
The seaweed polysaccharide alginic acid is a linear block copolymer composed of two uronic acid residues, namely D-mannuronic and L-guluronic acid.
The distribution of the uronic acids along the chain is non-random and involves relatively long sequences of each uronic acid.
In the presence of divalent cations, such as calcium, alginate gels can be formed due to ionic cross-linking via calcium bridges between L-guluronic acid residues on adjacent chains.
Alginates have historically been known to have a haemostatic function and to be capable of absorbing specific solutes.
Calcium alginate gels have a large pore size and high water absorbency making them potentially useful as hydrogel dressings.
Hydrophilic sponges (xerogels) produced from calcium alginate are reported to have good absorptive properties for both blood and wound exudate.
Alginate fibres are generally prepared by injecting a solution of water-soluble alginate (usually sodium alginate) into a bath containing an acidic solution or calcium salt solution to produce the corresponding alginic acid or calcium alginate fibres, which can be used to produce yarns and fabrics for medical applications, and as drug carriers for wound healing.
Alginate is a significant component of the biofilms produced by the bacterium Pseudomonas aeruginosa, a major pathogen found in the lungs of some people who have cystic fibrosis.
The biofilm and P. aeruginosa have a high resistance to antibiotics,and are susceptible to inhibition by macrophages.
Alginate is a natural product found in Sargassum fusiforme with data available.
Salts and esters of ALGINIC ACID that are used as HYDROGELS; DENTAL IMPRESSION MATERIALS, and as absorbent materials for surgical dressings (BANDAGES, HYDROCOLLOID).
They are also used to manufacture MICROSPHERES and NANOPARTICLES for DIAGNOSTIC REAGENT KITS and DRUG DELIVERY SYSTEMS.
Alginic acid exists in powder or filament form, or as amorphous granules of a yellowish white to brown color, insoluble in pure water and the various organic solvents.
Alginate can dissolve in water alkalized by sodium carbonate, sodium hydroxide or trisodium phosphate.
Alginic acid is a colloidal, hydrophilic polysaccharide obtained from certain brown algae by alkaline extraction.
Chances are that you frequently eat alginic acid.
Alginate can be found in some ice cream, cakes, salad dressings, and many other products.
Alginate is a great thickener, so it is frequently used in food.
Alginic acid comes from brown algae
Alginic acid is made up of D-mannuronic acid and L-guluronic acid structures connected with an alpha 1,4 bonds.
These two structures do not necessarily alternate from one to the other.
For example, a guluronate can be connected to another guluronate with an alpha 1,4 bond.
The exact number of mannuronates or guluronates in alginic acid isn't consistent.
Alginate naturally changes from one plant to another.
But, most often they occur in sets of two, so there will be two mannuronic acids connected with an alpha 1,4 bond, then connected to a guluronic acid with an alpha 1,4 bond which is connected to another guluronic acid with an alpha 1,4 bond.
This pattern will then repeat.
D-mannuronic acid is similar to D-mannose, only it has a COOH instead of a CH2 OH on carbon 6. And L-guluronic acid is similar to L-glucose, only, once again, it has a COOH instead of a CH2 OH on carbon 6.
Algin is a polysaccharide found in brown seaweeds, Phaeophyceae. Of those brown seaweeds, it is the kelp Macrocystis pyrifera that is primarily used in manufacture of Algin.
This specie is found mainly in North and South America, Australia, New Zealand, and Africa, and grows in calm waters and in large, dense beds.
Other seaweeds used in manufacture of Algin are Ascophyllum nodosum and Laminaria and Ecklonia.
The Algin in the kelp cell wall is a mixed salt (magnesium, calcium, sodium, potassium) of alginic acid.
Pure alginates dissolve in distilled water and form smooth solutions.
Alginates are compatible with other plant hydrocolloids as well as carbohydrates and proteins.
The uses of Alginates depend on their effective stabilizing, thickening, emulsifying, film forming, water-holding, and gelling properties.
There are several grades of sodium, potassium, calcium, ammonium, propylene glycol alginates, and alginic acid available.
Alginic acid is not an antacid, but because of its unique mechanism of action, Alginate is added to some antacid preparations to increase their effectiveness in the treatment and relief of the symptoms of GERD.
In the presence of saliva, alginic acid reacts with sodium bicarbonate to form sodium alginate.
Gastric acid causes this alginate to precipitate, forming a foaming, viscous gel that floats on the surface of the gastric contents.
This provides a relatively pH-neutral barrier during episodes of acid reflux and enhances the efficacy of drugs used to treat GERD.
Alginic acid products are not indicated for the treatment of PUD.
Alginic acid is a linear copolymer with homopolymeric blocks of (1→4)-linked β-D-mannuronate (M) and α-L-guluronate (G) residues, respectively, covalently linked together in different sequences or blocks.
The monomers may appear in homopolymeric blocks of consecutive G-residues (G-blocks), consecutive M-residues (M-blocks) or alternating M and G-residues (MG-blocks).
Note that α-L-guluronate is the C-5 epimer of β-D-mannuronate.
The uses of alginates are based on three main properties.
The first is their ability, when dissolved in water, to thicken the resulting solution (more technically described as their ability to increase the viscosity of aqueous solutions).
The second is their ability to form gels; gels form when a calcium salt is added to a solution of sodium alginate in water.
The gel forms by chemical reaction, the calcium displaces the sodium from the alginate, holds the long alginate molecules together and a gel is the result.
No heat is required and the gels do not melt when heated. This is in contrast to the agar gels where the water must be heated to about 80°C to dissolve the agar and the gel forms when cooled below about 40°C.
The third property of alginates is the ability to form films of sodium or calcium alginate and fibres of calcium alginates.
Alginate molecules are long chains that contain two different acidic components, abbreviated here for simplicity to M and G.
The way in which these M and G units are arranged in the chain and the overall ratio, M/G, of the two units in a chain can vary from one species of seaweed to another.
In other words all "alginates" are not necessarily the same.
So some seaweeds may produce an alginate that gives a high viscosity when dissolved in water, others may yield a low viscosity alginate.
The conditions of the extraction procedure can also affect viscosity, lowering Alginate if conditions are too severe.
All of this results in sellers normally offering a range of alginates with differing viscosities.
Similarly, the strength of the gel formed by the addition of calcium salts can vary from one alginate to another.
Generally alginates with a higher content of G will give a stronger gel; such alginates are said to have a low M/G ratio.
Some examples: Macrocystis can gives a medium-viscosity alginate, or a high viscosity with a careful extraction procedure (lower temperature for the extraction).
Sargassum usually gives a low viscosity product.
Laminaria digitata gives a soft to medium strength gel, while Laminaria hyperborea and Durvillaea give strong gels.
These are some of the reasons why alginate producers like to have a variety of seaweed sources, to match the alginate to the needs of particular applications.
The Laminaria is first extracted with water, and the residue with sodium carbonate; the filtrate is acidified with hydrochloric acid and the precipitated alginic acid washed and bleached.
Pharmaceutical and medical uses
If a fine jet of sodium alginate solution is forced into a bath of a calcium chloride solution, calcium alginate is formed as fibres.
If low viscosity alginates are used, a strong solution can be used without any viscosity problems and the calcium bath is not diluted as rapidly.
The fibres have very good strength when both wet and dry.
As with most polymer fibres formed by extrusion, stretching while forming increases the linearity of the polymer chains and the strength of the fibre.
Good quality stable fibres have been produced from mixed salts of sodium and calcium alginate, and processed into non-woven fabric that is used in wound dressings.
They have very good wound healing and haemostatic properties and can be absorbed by body fluids because the calcium in the fibre is exchanged for sodium from the body fluid to give a soluble sodium alginate.
This also makes Alginate easy to remove these dressings from large open wounds or burns since they do not adhere to the wound.
Removal can be assisted by applying saline solutions to the dressing to ensure Alginates conversion to soluble sodium alginate.
Recently, the consumer division of a multinational pharmaceutical company launched a new line of adhesive bandages and gauze pads based on calcium alginate fibres.
They are being promoted as helping blood to clot faster - twice as fast as their older, well established product.
Alginic acid powder swells when wetted with water.
This has led to its use as a tablet disintegrant for some specialized applications.
Alginic acid has also been used in some dietary foods, such as biscuits; Alginate swells in the stomach and, if sufficient is taken, Alginate gives a "full" feeling so the person is dissuaded from further eating.
The same property of swelling has been used in products such as Gavisconä tablets, which are taken to relieve heartburn and acid indigestion.
The swollen alginic acid helps to keep the gastric contents in place and reduce the likelihood of reflux irritating the lining of the oesophagus.
Alginate is used in the controlled release of medicinal drugs and other chemicals.
In some applications, the active ingredient is placed in a calcium alginate bead and slowly released as the bead is exposed in the appropriate environment.
More recently, oral controlled-release systems involving alginate microspheres, sometimes coated with chitosan to improve the mechanical strength, have been tested as a way of delivering various drugs.
Pronova Biomedical AS, a leading supplier of ultra-pure alginates and chitosans for controlled release and other medical materials applications, was acquired by FMC Bioploymer in early 2002; FMC had previously acquired Pronova Biopolymer, producer of food and technical grade alginates.
Alginate is used extensively as a mold-making material in dentistry, prosthetics, lifecasting, and in textiles.
Alginate 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 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.
Alginic acid is insoluble in water but becomes soluble when neutralized with alkali.
Medicinal tablets can be insoluble in the stomach but soluble in the bowels. To release the active medical ingredient properly in the bowels, tablets include alginic acid, a disintegrant, which swells in water.
Powders such as starch are commonly used but if alginic acid (a tablet disintegrant) is added, this produces tablets which show different properties from starch.
These tablets have a gastro resistance function as the alginic acid does not dissolve in the stomach acid and the tablets are subsequently delivered to the intestine.
Alginic acid begins to dissolve as the surrounding pH gradually increases in the intestine, where the tablets disintegrate and the active ingredient is released.
Alginic acid is important in designing tablets which are insoluble in the stomach and soluble in the intestines.
One common use for alginate is in cosmetics wherein Alginate is used for its functionality as a moisture retainer and thickener.
With these qualities, alginates have been used in several applications such as in retaining a lipstick’s color on the lip surface.
Alginate works so by the alginates forming a gel-like network that works on retaining the color of the lipstick.
The main use for alginate in the paper industry is in surface sizing.
Alginate added to the normal starch sizing gives a smooth continuous film and a surface with less fluffing.
The oil resistance of alginate films give a size with better oil resistance and enhances greaseproof properties.
An improved gloss is obtained with high gloss inks.
If papers or boards are to be waxed, alginate in the size will keep the wax mainly at the surface.
They give better coating runability than other thickeners, especially in hot, on-machine coating applications.
Alginates are also excellent film formers and improve ink holdout and printability.
The quantity of alginate used is usually 5-10 percent of the weight of starch in the size.
Alginate is also used in starch adhesives for making corrugated boards because Alginate stabilizes the viscosity of the adhesive and allows control of its rate of penetration.
One percent sodium alginate, based on the weight of starch used, is usually sufficient.
Paper coating methods and equipment have developed significantly since the late 1950s with the demand for a moderately priced coated paper for high quality printing.
Trailing blade coating equipment runs at 1 000 m/minute or more, so the coating material, usually clay plus a synthetic latex binder, must have consistent rheological properties under the conditions of coating.
Up to 1 percent alginate will prevent change in viscosity of the coating suspension under the high shear conditions where Alginate contacts the roller.
The alginate also helps to control water loss from the coating suspension into the paper, between the point where the coating is applied and the point where the excess is removed by the trailing blade.
The viscosity of the coating suspension must not be allowed to increase by loss of water into the paper because this leads to uneven removal by the trailing blade and streaking of the coating.
Medium to high viscosity alginates are used, at a rate of 0.4-0.8 percent of the clay solids.
Because of the solvent resistance of alginate films, the print quality of the finished paper is improved.
Coatings are applied to welding rods or electrodes to act as a flux and to control the conditions in the immediate vicinity of the weld, such as temperature or oxygen and hydrogen availability.
The dry ingredients of the coating are mixed with sodium silicate (water-glass) which gives some of the plasticity necessary for extrusion of the coating onto the rod; Alginate also acts as the binder for the dried coating on the rod.
However, the wet silicate has no binding action and does not provide sufficient lubrication to allow effective and smooth extrusion.
An additional lubricant is needed, and a binder that will hold the damp mass together before extrusion and maintain the shape of the coating on the rod during drying and baking.
Alginates are used to meet these requirements.
The quantities of alginates used are very dependent on the type of welding rod being coated and the extrusion equipment being used.
Alginate manufacturers are the best source of information for using alginates in weldig rod applications.
Binders for fish feed
The worldwide growth in aquaculture has led to the use of crude alginate as a binder in salmon and other fish feeds, especially moist feed made from fresh waste fish mixed with various dry components.
Alginate binding can lower consumption by up to 40 percent and pollution of culture ponds is sharply reduced.
The poor adhesion of films of alginate to many surfaces, together with their insolubility in nonaqueous solvents, have led to their use as mould release agents, originally for plaster moulds and later in the forming of fibreglass plastics.
Sodium alginate also makes a good coating for anti-tack paper, which is used as a release agent in the manufacture of synthetic resin decorative boards.
Films of calcium alginate, formed in situ on a paper, have been used to separate decorative laminates after they have been formed in a hot-pressing system.
In textile printing, alginates are used as thickeners for the paste containing the dye.
These pastes may be applied to the fabric by either screen or roller printing equipment.
Alginates became important thickeners with the advent of reactive dyes. These combine chemically with cellulose in the fabric.
Many of the usual thickeners, such as starch, react with the reactive dyes, and this leads to lower colour yields and sometimes by-products that are not easily washed out.
Alginates do not react with the dyes, they easily wash out of the finished textile and are the best thickeners for reactive dyes.
Alginates are more expensive than starch and recently starch manufacturers have made efforts to produce modified starches that do not react with the reactive dyes, so Alginate is becoming a more competitive market.
This use of alginate represents a large market, but Alginate is affected by economic recessions when there is often a fall in demand for clothing and textiles.
The types of alginate required vary from medium-to-high viscosity with older screen printing equipment, to low viscosity if modern, high speed, roller printing is used.
Textile printing accounts for about 50 percent of the global alginate market.
The thickening property of alginate is useful in sauces and in syrups and toppings for ice cream.
By thickening pie fillings with alginate, softening of the pastry by liquid from the filling is reduced.
Addition of alginate can make icings non-sticky and allow the baked goods to be covered with plastic wrap.
Water-in-oil emulsions such as mayonnaise and salad dressings are less likely to separate into their original oil and water phases if thickened with alginate.
Sodium alginate is not useful when the emulsion is acidic, because insoluble alginic acid forms; for these applications propylene glycol alginate (PGA) is used since this is stable in mild acid conditions.
Alginate improves the texture, body and sheen of yoghurt, but PGA is also used in the stabilization of milk proteins under acidic conditions, as found in some yoghurts.
Some fruit drinks have fruit pulp added and it is preferable to keep this in suspension; addition of sodium alginate, or PGA in acidic conditions, can prevent sedimentation of the pulp.
In chocolate milk, the cocoa can be kept in suspension by an alginate/phosphate mixture, although in this application it faces strong competition from carrageenan.
Small amounts of alginate can thicken and stabilize whipped cream.
For more information about factors that affect the viscosity of alginate solutions, see King (1983: 132-141).
This discusses the effects of concentration of alginate, Alginates molecular weight, the presence of any calcium remaining in the alginate from the extraction process, pH, temperature and other salts.
For a briefer discussion, see McHugh (1987) or Clare (1993).
Alginates have some applications that are not related to either their viscosity or gel properties.
They act as stabilizers in ice cream; addition of alginate reduces the formation of ice crystals during freezing, giving a smooth product.
This is especially important when ice cream softens between the supermarket and the home freezer; without alginate or similar stabilizer the refrozen ice cream develops large ice crystals, giving Alginate an undesirable crunchy mouth feel.
Alginate also reduces the rate at which the ice cream will melt.
Beer drinkers prefer some foam on the top of a newly-poured glass, and a poor foam leads to a subjective judgement that the beer is poor quality.
Addition of a very low concentration of propylene glycol alginate will provide a stable, longer lasting beer foam.
A variety of agents are used in the clarification of wine and removal of unwanted colouring - wine fining - but in more difficult cases Alginate has been found that the addition of sodium alginate can be effective.
The gelling properties of alginate were used in the first production of artificial cherries in 1946. A flavoured, coloured solution of sodium alginate was allowed to fall, in large drops, into a solution of a calcium salt.
Calcium alginate immediately formed as a skin on the outside of the drop and when the drop was allowed to sit in the solution, the calcium gradually penetrated the drop converting Alginate all into a gel that hardened with further standing.
Because the cherry-flavoured gels did not melt, they became very popular in bakery products.
Fruit substitutes can now be made by automated and continuous processes that are based on similar principles.
Either the calcium can be applied externally, as above, or internally.
In the latter case a calcium salt that does not dissolve is added to the fruit puree, together with a weak acid; the weak acid slowly attacks the calcium salt and releases water-soluble calcium that then reacts with the alginate and forms the gel.
Edible dessert jellies can be formed from alginate-calcium mixtures, often promoted as instant jellies or desserts because they are formed simply by mixing the powders with water or milk, no heat being required.
Because they do not melt, alginate jellies have a different, firmer mouth feel when compared to gelatin jellies, which can be made to soften and melt at body temperature.
Mixtures of calcium salts and sodium alginate can be made to set to a gel at different rates, depending on the rate at which the calcium salt dissolves.
Gel formation can also be delayed even after everything is mixed together; this is done using a gel-retarder that reacts with the calcium before the alginate does, so no calcium is available to the alginate until all the retarder is used.
In this way gel formation can be delayed for several minutes if desired, such as when other ingredients need to be added and mixed before the gel starts to set.
Alginate gels are used in re-structured or re-formed food products.
For example, re-structured meats can be made by taking meat pieces, binding them together and shaping them to resemble usual cuts of meat, such as nuggets, roasts, meat loaves, even steaks.
The binder can be a powder of sodium alginate, calcium carbonate, lactic acid and calcium lactate. When mixed with the raw meat they form a calcium alginate gel that binds the meat pieces together.
This is used for meats for human consumption, such as chicken nuggets; Alginate has become especially useful in making loaves of meat for fresh pet food; some abattoir wastes are suitable and cheap ingredients.
Up to 1 percent alginate is used.
Similar principles are applied to making shrimp substitutes using alginate, proteins such as soy protein concentrate, and flavours.
The mixture is extruded into a calcium chloride bath to form edible fibres which are chopped, coated with sodium alginate and shaped in a mould.
Restructured fish fillets have been made using minced fish and a calcium alginate gel.
Onion rings are made from dried onion powder; pimento olive fillings are made using pimento pulp.
In 2001, a new line of olives launched in Spain were stuffed with flavoured pastes, such as garlic, herbs, hot pepper, lemon and cheese.
Each of these is made with green manzanilla olives and an alginate-based paste containing the appropriate ingredient to provide the flavour.
Calcium alginate films and coatings have been used to help preserve frozen fish.
The oils in oily fish such as herring and mackerel can become rancid through oxidation even when quick frozen and stored at low temperatures.
If the fish is frozen in a calcium alginate jelly, the fish is protected from the air and rancidity from oxidation is very limited.
The jelly thaws with the fish so they are easily separated.
If beef cuts are coated with calcium alginate films before freezing, the meat juices released during thaw are re-absorbed into the meat and the coating also helps to protect the meat from bacterial contamination.
If desired, the calcium alginate coating can be removed by re-dissolving it with sodium polyphosphate.
Alginic acid is used in wheat flour products like noodles and bread to improve the product quality.
Adding alginic acid to flour dough helps water retention and gives a soft texture to products.
Alginic acid also has an effect on starch and proteins in wheat flour causing reinforcement of the dough structure after cooking or baking.
A straight chain, hydrophilic, colloidal polyuronic acid Alginic acid is used as a precursor for the preparation of sodium alginate, potassium alginate and calcium alginate, which finds application in various industries such as food, textile printing and pharmaceuticals.
Alginate acts as an additive in dehydrated products such as slimming aids.
Alginate is also used in the production of paper and textiles.
Alginate is actively involved in waterproofing, fireproofing fabrics.
Alginate utilized as a thickening agent in drinks, ice cream and cosmetics.
Alginate plays an important role as a raw material for the synthesis of propylene glycol alginate and polysaccharide sulfate.
Alginate is also useful to treat and purify waste water having strong absorbility.
Alginic acid is used for prohibited purposes
The 2015 Technical Review (TR) says, “Alginic acid is primarily used to improve textures in soups and soup mixes as an emulsifier, formulation aid, stabilizer and thickener.
The use of alginic acid for these purposes is not a response to flavors, colors, textures or nutritive values lost in processing, but is used instead to improve textures of soup and soup mixes as sold.” Is it better
To provide an artificial texture? We believe that purpose is not consistent with consumer expectation of organic products.
Alginates are salts of the long-chain, carbohydrate biopolymer alginic acid.
They are extracted from various species of brown algae (seaweed) and purified to a white powder.
The alginates have different characteristics of viscosity and reactivity based on the specific algal source and the ions in solution.
Alginic acid is insoluble, but the salts are hydrocolloids (materials that bind or absorb water).
The common salts used in the food and pharmaceutical industries are sodium alginate, potassium alginate, and propylene glycol alginate.
Alginates are generally acid stable and heat resistant.
Adjusting the concentration of calcium ions (which cause crosslinking), controls gel strength, and combining alginate with other gums, such as pectin, increases viscosity dramatically.
Dispersing low concentrations of alginate is usually easy in ambient temperature water, but hard or very cold water makes it more difficult.
Alginate concentrations above 2% require high shear mixing to eliminate clumps and fisheyes.
Both the Rotosolver and Rotostat are ideal for in-tank processing to quickly dispersing alginate without forming clumps.
These sanitary high-speed mixers combine high flow with high shear to increase mixing efficiency and productivity.
For your inline powder induction and dispersion requirements, learn more about the Fastfeed and Dynashear.
Alginate is popular as a thickener, stabilizer, emulsifier, coating and gelling agent in several applications:
Used by printers in inks and textile dyes
pharmaceutical manufacturers use as a binder or time-released agent to produce gelcaps, active encapsulants, film formers in antacids, or dressings along with CMC
beverage processors use it to add body and stabilize foam
to thicken and stabilize salad dressing emulsions
to add body and prevent crystal growth in ice cream
form gels for jellies and pie fillings
to improve texture and hunger satisfaction in low calorie formulations
to hold moisture and keep baked goods fresh
Alginate is used in various pharmaceutical preparations.
Chemically, Alginate is a linear copolymer with homopolymeric blocks of (1-4)-linked ?-D-mannuronate (M) and its C-5 epimer ?-L-guluronate (G) residues, respectively, covalently linked together in different sequences or blocks.
Alginic acid can be separated from benzoate, citric acid and saccharin by mixed-mode chromatography on Primesep C HPLC column.
This method can be used to quantitate alginic acid, citric acid or saccharin in complex mixtures.
Various detection technique can be used (UV, ELSD, LC/MS), based on mobile phase selection.
Alginates are refined from brown seaweeds.
Throughout the world, many of the Phaeophyceae class brown seaweeds are harvested to be processed and converted into sodium alginate.
Sodium alginate is used in many industries including food, animal food, fertilisers, textile printing, and pharmaceuticals.
Dental impression material uses alginate as Alginates means of gelling.
Food grade alginate is an approved ingredient in processed and manufactured foods.
Brown seaweeds range in size from the giant kelp Macrocystis pyrifera which can be 20–40 meters long, to thick, leather-like seaweeds from 2–4 m long, to smaller species 30–60 cm long.
Most brown seaweed used for alginates are gathered from the wild, with the exception of Laminaria japonica, which is cultivated in China for food and Alginates surplus material is diverted to the alginate industry in China.
Alginates from different species of brown seaweed vary in their chemical structure resulting in different physical properties of alginates.
Some species yield an alginate that gives a strong gel, another a weaker gel, some may produce a cream or white alginate, while others are difficult to gel and are best used for technical applications where color does not matter.
Commercial grade alginate are extracted from giant kelp Macrocystis pyrifera, Ascophyllum nodosum, and types of Laminaria.
Alginates are also produced by two bacterial genera Pseudomonas and Azotobacter, which played a major role in the unravelling of Alginates biosynthesis pathway.
Bacterial alginates are useful for the production of micro- or nanostructures suitable for medical applications.
Sodium alginate (NaC6H7O6) is the sodium salt of alginic acid.
Potassium alginate (KC6H7O6) is the potassium salt of alginic acid.
Calcium alginate (CaC12H14O12), is made from sodium alginate from which the sodium ion has been removed and replaced with calcium (ion exchange).
Various grades of alginic acid are commercially available that vary in their molecular weighs and hence viscosity.
Viscosity increases considerably with increasing concentration; typically a 0.5% w/w aqueous dispersion will have a viscosity of approximately 20 mPas, while a 2.0% w/w aqueous dispersion will have a viscosity of approximately 2000, mPas.
The viscosity of dispersions decreases with increasing temperature.
As a general rule, a 10C increase in temperature results in a
2.5% reduction in viscosity.
At low concentrations, the viscosity of an alginic acid dispersion may be increased by the addition of a calcium salt, such as calcium citrate.
Chemical and Physical Properties
Property Name and Property Value
Molecular Weight: 418.23
Hydrogen Bond Donor Count: 6
Hydrogen Bond Acceptor Count: 12
Rotatable Bond Count: 5
Exact Mass: 418.04300006
Monoisotopic Mass: 418.04300006
Topological Polar Surface Area: 192 Å²
Heavy Atom Count: 26
Formal Charge: 0
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 10
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count: 0
Covalently-Bonded Unit Count: 1
Compound Is Canonicalized: Yes
Boiling Point: 716.00to718.00°C.@760.00mmHg
Solubility: 1e+006 mg/L @ 25 °C (est)
LogP: -3.203 (est)
Appearance: White to Light yellow to Dark green powder to crystal
Neutralization Value: 200.0 to 260.0(calcd.on dried substance)
Drying loss: max. 15.0 %
Ignition residue(Sulfate): max. 12.0 %
Physical State:Low-Melting Solid
Solubility: Soluble in 0.1 M NaOH, and alkaline solutions.
Insoluble in water(but swells), and organic solvents.
Storage: Store at room temperature
Melting Point: >300° C
Boiling Point: 495.24° C at 760 mmHg
Density: 1.99 g/cm3
Refractive Index: n20D 1.69
Properties of the Substance:
Alginic acid is an odorless, white to yellowish-white fibrous powder that is insoluble in water and organic solvents, and slightly soluble in alkali solutions (Remington, et al. 1975; FAO 2003).
A tasteless substance, alginic acid carries a pH between 2.0 and 3.4 in a 3% solution (Merck and Co., Inc. 1976).
Summary of Petitioned Use
Alginic acid is currently listed in 7 CFR Section 205.605(a) as a nonagricultural (nonorganic), nonsynthetic substance allowed as an ingredient in or on processed products labeled as “organic” or “made with organic (specified ingredients or food group(s))” in the National List of Allowed and Prohibited Substances (hereafter referred to as the National List) (USDA National Organic Program 2014).
Alginic acid is defined by the Food and Drug Administration (FDA) as a “colloidal, hydrophilic polysaccharide obtained from certain brown algae by alkali extraction (FDA 2014)” and is classified as a food hydrocolloid along with other materials such as gum arabic, guar gum and carrageenan (Imeson 2010).
Alginic acid is “a hydrophilic, colloidal polysaccharide obtained from seaweeds,” which means Alginate is a water loving multi-chain carbohydrate (it can absorb 200-300 times its weight of water and salts) whose insoluble particles are dispersed throughout another substance, in this case water (Merck and Co., Inc. 1976).
A natural polysaccharide, alginic acid is an unbranched binary copolymer consisting of (1,4)-linked β -d-mannuronic acid and α -l-guluronic acid, which are often referred to as M and G blocks respectively
when found in consecutive units and MG blocks when found in alternating sequences (Liu, et al. 2006).
Alginic acid is able to absorb and chemically bind sodium and other cations when prepared or ingested (Merck and Co., Inc. 1976; R.E. Gosselin 1976; FAO 2003).
The chemical formula for alginic acid is (C6H8O6)n where n is the number of repeated molecular units to form the saccharide chain.
The melting point of the substance is 300 °C (Sigma-Aldrich Co. LLC 2014).
The manufacturing process used to extract sodium alginates from brown seaweed fall into two categories: 1) calcium alginate method and, 2) alginic acid method.
Chemically the process is simple, but difficulties arise from the physical separations required between the slimy residues from viscous solutions and the separation of gelatinous precipitates that hold large amounts of liquid within their structure, so they resist filtration and centrifugation.
Since alginic acid is insoluble in water, Alginate alone does not function as a thickener or gelling agent.
In order to dissolve alginic acid in water, Alginate is necessary to neutralize by adding alkali.
Alginic acid is soluble by making a salt with monovalent cations such as Na and K.
Alginic acid becomes insoluble by making a salt with polyvalent cations like Ca and Fe.
Alginic acid does not dissolve in water.
However, special processing can be used to make a type of alginic acid that easily absorbs water and swells.
This swelling type of alginic acid increases its apparent viscosity when it absorbs water and becomes a swelled liquid similar to starch paste.
Thus, alginic acid can be broadly divided into two types: swelling and non-swelling.
Alginic acid is known to be more susceptible to heat than sodium alginate and other alginate salts.
Alginates molecular weight (degree of polymerization) decreases over a short period of time.
In order to maintain molecular weight, storage at the lowest temperature possible is required.
Alginate absorbs water quickly, which makes Alginate useful as an additive in dehydrated products such as slimming aids, and in the manufacture of paper and textiles.
Alginate is also used for waterproofing and fireproofing fabrics, in the food industry as a thickening agent for drinks, ice cream, cosmetics, and as a gelling agent for jellies.
Sodium alginate is mixed with soybean flour to make meat analogue.
Alginate is used as an ingredient in various pharmaceutical preparations, such as Gaviscon, in which it combines with bicarbonate to inhibit gastroesophageal reflux.
Sodium alginate is used as an impression-making material in dentistry, prosthetics, lifecasting, and for creating positives for small-scale casting.
Sodium alginate is used in reactive dye printing and as a thickener for reactive dyes in textile screen-printing. Alginates do not react with these dyes and wash out easily, unlike starch-based thickeners.
Alginate also serves as a material for micro-encapsulation.
Calcium alginate is used in different types of medical products, including skin wound dressings to promote healing, and may be removed with less pain than conventional dressings.
Alginic acid is suitable reagent used to study the in-vitro and in-vivo mitogenic activity of alginates.
Alginate is suitable for use in the spectrophotometric determination of transparent exopolymer particles by dye-binding assay.
Specific Uses of the Substance:
The FDA has identified alginic acid as Generally Recognized as Safe (GRAS) and allowed for use only as an emulsifier, emulsifier salt, formulation aid, stabilizer and thickener (FDA 2014).
The use of alginic acid is limited to soups and soup mixes (FDA 2014).
Any use of alginic acid outside of these limitations would require additional rule making either through a food additive regulation or amendment to the GRAS affirmation regulation.
Alginic acid is insoluble in water and is not often added directly to food, but Alginate is used extensively for non-food uses in the pharmaceutical industry as a tablet disintegrant due to Alginates ability to swell in water (Saltmarsh, Barlow and eds. 2013).
Approved Legal Uses of the Substance:
Alginic acid is a nonagricultural (nonorganic), nonsynthetic substance allowed as an ingredient in or on processed products labeled as “organic” or “made with organic (specified ingredients or food group(s))” in the National List (USDA National Organic Program 2014).
Alginic acid is listed at 21 CFR 184.1011 as a direct food substance affirmed as GRAS with specific limitations for use as an emulsifier, emulsifier salt, formulation aid, stabilizer and thickener in soups and soup mixes (FDA 2014).
Alginic acid is listed by the EPA as both an inert material approved for use in non-food use pesticides (EPA 2010) and as a former List 3 inert of unknown toxicity as included on the list of inert ingredients last updated in August of 2004 (EPA 2004).
Alginic acid reduces reflux via its floating, foaming, and viscous properties.
Alginic acid precipitates upon contact with gastric acid to create a mechanical barrier, or a "raft", that displaces the postprandial acid pocket.
The formation of a raft is thought to occur rapidly, often within a few seconds of dosing.
In clinical trials, alginic acid was effective in reducing the symptoms of gastroesophageal reflux disease (GERD).
In healthy volunteers, alginic acid in combination with an antacid was effective in decreasing postprandial reflux in the upright position.
Alginic acid is able to bind to cations when ingested.
The absorption into the systemic circulation from oral formulations of alginic acid is reported to be minimal, as the mode of action of alginic acid is physical.
This pharmacokinetic parameter is unlikely to apply for alginic acid.
This pharmacokinetic parameter is unlikely to apply for alginic acid.
Mechanism of Action
Once orally administered, alginic acid reacts with gastric acid to form a floating "raft" of alginic acid gel on the gastric acid pool.
Alginate-based raft-forming formulations commonly contain sodium or bicarbonate; bicarbonate ions are converted to carbon dioxide in presence of gastric acid and get entrapped within the gel precipitate, converting it into a foam which floats on the surface of the gastric contents, much like a raft on water.
The "raft" has a near neutral pH due to carbon dioxide and floats on the stomach contents and potentially functions as a barrier to impede gastroesophageal reflux.
In severe cases, the raft itself may be refluxed into the oesophagus in preference to the stomach contents and exert a demulcent effect.
Alginate may be used in a hydrogel consisting of microparticles or bulk gels combined with nerve growth factor in bioengineering research to stimulate brain tissue for possible regeneration.
In research on bone reconstruction, alginate composites have favorable properties encouraging regeneration, such as improved porosity, cell proliferation, and mechanical strength, among other characteristics.
Alginate hydrogel is a common biomaterial for bio-fabrication of scaffolds and tissue regeneration.
Action of the Substance:
Due to Alginates hydrophilic nature and high insolubility in water, alginic acid is used to manufacture pharmaceutical tablets that deliver probiotics and drugs (Saltmarsh, Barlow and eds. 2013).
Alginic acid is also used as an emulsifier, emulsifier salt, formulation aid, stabilizer or thickener according to FDA limitations described earlier (Saltmarsh, Barlow and eds. 2013; FDA 2014).
Alginate is not often added directly to food, however, but rather is created in situ when sodium alginate is added to acidic foods (Saltmarsh, Barlow and eds. 2013), with the lower pH causing alginic acid to precipitate from the solution (FAO 2003; Green 1934).
The newly created alginic acid will form a gelatinous film due to Alginates insolubility in water (Saltmarsh, Barlow and eds. 2013).
The action of alginic acid is directly related to the amounts of M, G and MG blocks present in the co101 polymer (Kloareg and Quatrano 1988).
Alginic acid with low M/G ratio and high guluronic acid content form strong and rigid gels (Kloareg and Quatrano 1988; Kim 2011).
Alternatively, alginic acids with high M/G ratio and low guluronic acid content will form soft, elastic gel (Kloareg and Quatrano 1988; Kim 2011).
Chewable tab containing alginic acid, Ca carbonate, and heavy Mg carbonate: Hypercalcaemia or conditions resulting in hypercalcaemia; hypercalciuria, nephrolithiasis (due to calculi-containing Ca deposits), pre-existing hypophosphataemia.
Severe renal impairment.
Alginate consists chiefly of sodium salt of alginic acid, polyuronic acid composed of beta d-mannuronic acid residues linked so that carboxyl group of each unit is free while aldehyde group is shielded by glycosidic linkage.
All derivatives of alginic acid designated by the generic term algin.
Most commonly used algin compound is sodium alginate often used interchangeably.
Trade names include alginate, sfc; cecalgum, sanofi; dialgin, diamalt; keltex, kelco; lamitex, protan; manutex, kelco. dental alginates are powder mixtures with the following composition: sodium alginate (10 ? 20 wt %), calcium sulfate (10 wt %), trisodium phosphate (1 ? 4 wt %), diatomite (70 ? 80 wt %), color and flavor (1 ? 2 wt %).
Patient with fluid retention.
Chewable tab containing alginic acid, Ca carbonate, and heavy Mg carbonate: Patient with constipation, haemorrhoids, sarcoidosis. Not indicated for long-term treatment.
Renal impairment. Children. Pregnancy and lactation.
Alginic acid method
When acid is added to the filtered extract, alginic acid forms in soft, gelatinous pieces that must be separated from the water.
Again flotation is often used; filtration is not possible because of the soft jelly-like nature of the solid.
If an excess of sodium carbonate is used in the original extraction, this will still be present in the filtered extract so that when acid is added, carbon dioxide will form.
Fine bubbles of this gas attach themselves to the pieces of alginic acid and lift them to the surface where they can be continuously scrapped away.
The processor now has a jelly-like mass of alginic acid that actually contains only 1-2 percent alginic acid, with 98-99 percent water.
Somehow, this water content must be reduced.
Alginic acid is too soft to allow the use of a screw press.
Some processors place the gel in basket-type centrifuges lined with filter cloth.
Centrifuging can increase the solids to 7-8 percent and this is sufficient if alcohol is to be used in the next step of converting it to sodium alginate.
Alginic acid is also now sufficiently firm to be squeezed in a screw press.
The 7-8 percent alginic acid is place in a mixer and, allowing for the water contained in the alginic acid, enough alcohol (usually ethanol or isopropanol) is added to give a 50:50 mixture of alcohol and water.
Then solid sodium carbonate is added gradually until the resulting paste reaches the desired pH.
The paste of sodium alginate can be extruded as pellets, oven dried and milled.
IUPAC Name: 3-(6-carboxy-3,4-dihydroxy-5-phosphanyloxan-2-yl)oxy-4,5-dihydroxy-6-phosphanyloxyoxane-2-carboxylic acid
InChI Key: FHVDTGUDJYJELY-UHFFFAOYSA-N
Canonical SMILES: C1(C(C(OC(C1OC2C(C(C(C(O2)C(=O)O)P)O)O)C(=O)O)OP)O)O
Molecular Formula: C12H20O12P2
CompTox Dashboard (EPA): DTXSID601010868
ECHA InfoCard: 100.029.697
A02BX13 - alginic acid ; Belongs to the class of other drugs used in the treatment of peptic ulcer and gastro-oesophageal reflux disease (GERD).
Alginate, Sodium Calcium
Alginic acid, barium salt
Alginic acid, calcium salt
Alginic acid, copper salt
Alginic acid, potassium salt
Alginic acid, sodium salt
Calcium Alginate, Sodium
Poly(mannuronic acid), sodium salt
Sodium calcium alginate