Carrageenan

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This article is about algal polysaccharides. For the personal lubricant brand Carrageenan, see Oceanus carrageenan.

Carrageenans or carrageenins (pronounced [ˌkærəˈgiːnəns]) are a family of linear sulphated polysaccharides extracted from red seaweeds. The name is derived from a type of seaweed that is abundant along the Irish coastline near the village of Carragheen. Gelatinous extracts of carrageen seaweed (also known as Irish moss) have been used as food additives for hundreds of years ^[1]. Research has raised concerns about the health implications of carrageenan consumption.

1 Uses
2 Health concerns
3 Trivia
4 See also
5 References

[edit] Uses

Carrageenans are large, highly flexible molecules which curl forming helical structures. This gives them the ability to form a variety of different gels at room temperature. They are widely used in the food and other industries as thickening and stabilizing agents. A particular advantage is that they are thixotropic—they thin under shear stress and recover their viscosity once the stress is removed. This means that they are easy to pump but stiffen again afterwards.

For example, they can be used in:

Desserts, ice cream, milk shakes, sauces - gel to increase viscosity, PayDay bars contain carrageenans.
Beer - clarifier to remove haze-causing proteins
Pâtés and processed meat - Substitute fat to increase water retention and increase volume
Toothpaste - stabilizer to prevent constituents separating
Fire fighting foam - thickener to cause foam to become sticky
Shampoo and cosmetic creams - thickener
Air freshener gels
Shoe polish - gel to increase viscosity
Biotechnology - gel to immobilize cells/enzymes
Personal lubricants - laboratory studies suggest that carrageenans might function as a topical microbicides, blocking sexually-transmitted viruses such as HIV, HPV and herpes ^[2]^[3]

Lambda carrageenan is used in animal models of inflammation used to test analgesics. Dilute carrageenan solution (1-2%) injected subcutaneously causes swelling and pain.

There are three main commercial classes of carrageenan:

Kappa - strong, rigid gels. Produced from Kappaphycus cottonii
Iota - soft gels. Produced from Eucheuma spinosum
Lambda - form gels when mixed with proteins rather than water, used to thicken dairy products. The most common source is Gigartina from Southern Europe.

It is interesting to note, however, that a lot of red algal species produce different types of carrageenans during their developmental history. For instance, the genera Gigartina produces mainly Kappa carrageenans during its gametophytic stage, and Lambda carrageenans during its sporophytic stage.

See also: Alternation of generations

All are soluble in hot water, but in cold water only the Lambda form (and the sodium salts of the other two) are soluble.

When used in food products, carrageenan has the EU additive E-number E407. Although introduced on an industrial scale in the 1930s, the first use was in China around 600 BC (where Gigartina was used) and in Ireland around 400 AD.

The largest producer is the Philippines, where cultivated seaweed produces about 80% of the world supply. The most commonly used are Cottonii (Eucheuma cottonii) and Spinosum (Eucheuma spinosum), which together provide about three quarters of the World production. These grow at sea level down to about 2 metres. The seaweed is normally grown on nylon lines strung between bamboo floats and harvested after three months or so when each plant weighs around 1 kg.

The Cottonii variety has been reclassified as Kappaphycus cottonii by Maxwell Doty (1988), thereby introducing the genus Kappaphycus, on the basis of the phycocolloids produced (namely kappa carrageenan).

After harvest, the seaweed is dried, baled, and sent to the carrageenan manufacturer. There the seaweed is ground, sifted to remove impurities such as sand, and washed thoroughly. Next, the cellulose is removed from the carrageenan by centrifugation and filtration. The resulting carrageenan solution is then concentrated by evaporation. It is dried and ground to specification.

[edit] Health concerns

There is evidence from studies performed on rats, guinea pigs and monkeys which indicates that degraded carrageenan (poligeenan) may cause ulcerations in the gastro-intestinal tract and gastro-intestinal cancer ^[4]. Poligeenan is produced from carrageenan subjected to high temperatures and acidity. The average carrageenan molecule weighs over 100,000 Da while poligeenans have a molecular weight of less than 50 kDa. A scientific committee working on behalf of the European Commission has recommended that the amount of degraded carrageenan be limited to a maximum of 5% (which is the limit of detection) of total carrageenan mass. Upon testing samples of foods containing high molecular weight carrageens, researchers found no poligeenan. [1]