Carrageenan
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'''Carrageenans''' or '''carrageenins''' ({{pronEng|ˌkærəˈgiːnənz}}) are a family of linear sulphated [[polysaccharide]]s extracted from red [[seaweed]]s. The name is derived from a type of seaweed that is abundant along the [[Ireland|Irish]] coastline. Gelatinous extracts of the ''[[Chondrus crispus]]'' seaweed have been used as food additives for hundreds of years,<ref>[http://www.fao.org/docrep/field/003/AB730E/AB730E03.htm FAO Agar and Carrageenan Manual]</ref> though analysis of carrageenan safety as an additive continues.<ref>[http://www.who.int/ipcs/food/jecfa/summaries/summary68.pdf Joint FAO/WHO Expert Committee on Food Additives]</ref>
== Properties ==
Carrageenans are large, highly flexible molecules which curl forming [[helix|helical]] structures. This gives them the ability to form a variety of different [[gel]]s at room temperature. They are widely used in the food and other industries as [[Thickening agent|thickening]] and [[stabilizing agent]]s. A particular advantage is that they are [[Non-Newtonian fluid|pseudoplastic]] — 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.
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 [[protein]]s rather than water, used to thicken dairy products. The most common source is ''Gigartina'' from Southern Europe.
Many red algal species produce different types of carrageenans during their developmental history. For instance, the genus ''Gigartina'' produces mainly Kappa carrageenans during its [[gametophytic]] stage, and Lambda carrageenans during its [[sporophytic]] stage. See [[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 [[European Union|EU]] additive [[E-numbers|E-number]] E407 or E407a when present as "Processed eucheuma seaweed". 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 (''Kappaphycus alvarezii, K.striatum'') and Spinosum (''Eucheuma denticulatum''), 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. After treatment with hot [[alkali]] solution (e.g. 5-8% [[potassium hydroxide]]), 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.
== Uses ==
* [[Dessert]]s, [[ice cream]], milk shakes, sweetened [[condensed milk]]s, [[sauce]]s — gel to increase viscosity
* [[Beer]] — clarifier to remove haze-causing proteins
* [[Pâté]]s 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
* [[Marbling]] -- the ancient art of paper and fabric marbling uses a carrageenan mixuture to float paints or inks upon; the paper or fabric is then laid on it, absorbing the colors.
* Shoe polish — gel to increase [[viscosity]]
* [[Biotechnology]] — gel to immobilize cells/enzymes
* Pharmaceuticals — used as an inactive [[excipient]] in pills/tablets
* Carrageenan has also been used to thicken skim milk, in an attempt to emulate the consistency of whole milk. This usage did not become popular. It's used in some brands of [[soy milk]]
* [[Diet soda]]s
* Lambda carrageenan is used in animal models of inflammation used to test analgesics, because dilute carrageenan solution (1-2%) injected subcutaneously causes swelling and pain.
=== Sexual lubricant and microbicide ===<!-- This section is linked from [[Human papillomavirus]] -->
Laboratory studies suggest that carrageenans might function as [[Microbicides for sexually transmitted diseases|topical microbicide]]s, blocking [[Sexually transmitted disease|sexually transmitted viruses]] such as [[HPV]] and [[Herpes simplex virus|herpes]], though not HIV.
==== HSV ====
There are indications that a carrageenan-based gel may offer some protection against HSV-2 transmission by binding to the receptors on the herpes virus thus preventing the virus from binding to cells. Researchers have shown that a carrageenan-based gel effectively prevented HSV-2 infection at a rate of 85% in a mouse model. See [[Herpes simplex#Polysaccharides|Herpes simplex: Polysaccharides]]
==== HPV ====
A study published in August 2006 found it potentially a thousand times as effective against [[Human papillomavirus|HPV]] (measuring ''[[in vitro]]'' infectivity of [[pseudovirus]]es, which are believed to mimic the activity of actual viruses). If effective, its cost compared to [[HPV vaccine]]s and its ability to target any strain of the virus would make it an attractive prevention measure against cervical cancer, especially in developing countries.<ref name="carraguard">{{Cite web
| title = Microbicides
| work = Population Council
| accessdate = 2007-09-05
| date = [[2007-08-23]]
| url = http://www.popcouncil.org/microbicides/index.html
}}</ref> Some [[personal lubricant|personal]] and [[condom]] lubricants are already made with carrageenan, and several of these products (such as [http://www.bioglide.com/en/index.html Bioglide] and [[Divine No. 9|Divine]]) were found to be potent HPV inhibitors in the study (though others that listed carrageenan in their ingredients were not).<ref>{{Cite journal
| doi = 10.1371/journal.ppat.0020069
| volume = 2
| issue = 7
| pages = e69
| last = Buck
| first = Christopher B
| coauthors = Cynthia D Thompson, Jeffrey N Roberts, Martin Müller, Douglas R Lowy, John T Schiller
| title = Carrageenan Is a Potent Inhibitor of Papillomavirus Infection
| journal = PLoS Pathogens
| date = 2006
}}</ref>
Although the researchers are optimistic and show that the products "block HPV infectivity in vitro, even when diluted a million-fold", they emphasize that "it would be inappropriate to recommend currently available products for use as topical microbicides" until further human tests are complete. (By comparison, similarly optimistic results were expected for HIV prevention by [[cellulose sulfate]] gels, based on early tests, but the clinical trials had to be halted when the gel was found to ''increase'' incidence of HIV infection.)<ref>[http://www.sciencedaily.com/releases/2007/02/070201235814.htm Organization Halts Clinical Trial For Potential Microbicide For Preventing HIV Infection]</ref>
The researchers then tested HPV infectivity in mice. This study, released in July 2007, also found promising results, preventing infection ''[[in vivo]]'' by HPV-16 pseudoviruses even in the presence of [[nonoxynol-9]], which was shown to greatly increase infection when used alone.<ref>{{Cite journal
| doi = 10.1038/nm1598
| issn = 1078-8956
| volume = 13
| issue = 7
| pages = 857–861
| last = Roberts
| first = Jeffrey N
| coauthors = Christopher B Buck, Cynthia D Thompson, Rhonda Kines, Marcelino Bernardo, Peter L Choyke, Douglas R Lowy, John T Schiller
| title = Genital transmission of HPV in a mouse model is potentiated by nonoxynol-9 and inhibited by carrageenan
| journal = Nat Med
| accessdate = 2007-09-05
| year = 2007
| month = July
}}</ref> The results for the carrageenan tests (including those with Divine and Bioglide commercial lubricants) showed no detectable infection, while the viscous [[Scientific control|control]] gel and N-9 gels did.<ref>"Carrageenan prevented infection in the genital mucosa rendered susceptible to infection by either mechanical disruption (Cytobrush) or chemical disruption (N-9). Two commercial carrageenan-containing lubricants (Divine No. 9 and BIOglide) that showed strong inhibitory activity in an ''in vitro'' pseudovirus assay similarly prevented detectable infection ''in vivo''."</ref><ref>[http://www.nature.com/nm/journal/v13/n7/images/nm1598-F2.jpg Graphic summary of results]</ref>
While effectiveness trials have not been completed and side effects have not been ruled out, companies are already planning to capitalize on the discovery, such as Dreamspan naming their lubricant ''Carrageenan'' after its principal ingredient.<ref>Arizona Republic [http://www.azcentral.com/arizonarepublic/business/articles/0809biz-innovator0809.html article] about the development of Carrageenan.</ref><ref>[http://www.dreamspan-pi.com/ Dreamspan Product Innovation], manufacturer of Carrageenan</ref><ref>[http://www.antiviralgel.com/ An All Natural Anti Viral Red Marine Algae Sex Gel<!-- Bot generated title -->]</ref>
==== HIV ====
A phase 3 [[clinical trial]] by [[Population Council]] examined whether a carrageenan-based product known as ''Carraguard'' was effective as a [[topical microbicide]] for blocking HIV infection in women.<ref name="carraguard"/> The trial ran from 2004 to 2007, with more than 4,000 [[South Africa]]n women completing the study, but found no statistical difference in infection between those who used the lubricant and those who did not.<ref>{{Cite web
| title = Trial Shows Anti-HIV Microbicide Is Safe, but does Not Prove it Effective
| work = Population Council
| accessdate = 2008-03-12
| date = 2008-02-18
| url = http://www.popcouncil.org/mediacenter/newsreleases/Carraguard_Findings.html
}}</ref><ref>
{{Cite web
| title = Experimental Microbicide Carraguard Does Not Provide Protection Against HIV, Study Finds
| work = kaisernetwork.org
| accessdate = 2008-03-12
| date = 2008-02-20
| url = http://www.kaisernetwork.org/Daily_reports/rep_index.cfm?DR_ID=50494
}}</ref> The trial did provide information about usage patterns, however, and showed that the gel is safe at least - not increasing infection any more than the baseline or causing significant side effects. As such, they expect to use it as a stable delivery vehicle for experimental [[antiretroviral]]s in future studies.
== Health concerns ==
There is evidence from studies performed on [[rat]]s, [[guinea pig]]s and [[monkey]]s which indicates that degraded carrageenan (poligeenan) may cause ulcerations in the gastro-intestinal tract and [[gastro-intestinal tract|gastro-intestinal]] [[Cancer (medicine)|cancer]].<ref>[http://www.ehponline.org/members/2001/109p983-994tobacman/tobacman-full.html Review of harmful gastrointestinal effects of carrageenan in animal experiments] J. K. Tobacman. Environ Health Perspect. (2001) 109(10):983</ref> Poligeenan is produced from carrageenan subjected to high [[temperature]]s and [[acid]]ity. The average carrageenan molecule weighs over 100,000 [[Dalton (unit)|Da]] while poligeenans have a [[molecular weight]] of less than 50,000 [[Dalton (unit)|Da]]. 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.<ref>[http://www.cybercolloids.net/news/EU-carrageenan-opinion.pdf Opinion of the Scientific Committee on Food on Carrageenan] - 5 March 2003</ref>
A recent publication<ref>[http://ajpgi.physiology.org/cgi/content/full/292/3/G829 Carrageenan induces interleukin-8 production through distinct Bcl10 pathway in normal human colonic epithelial cells] Borthakur A. et al. Am J Physiol Gastrointest Liver Physiol (2007) 292:G829-G838</ref> indicates that carrageenan induces inflammation in human intestinal epithelial cells in tissue culture through a [[BCL10]]-mediated pathway that leads to activation of [[NFkappaB]] and [[IL-8]]. Carrageenan may be [[immunogenicity|immunogenic]] due to its unusual alpha-1,3-galactosidic link that is part of its disaccharide unit structure. Consumption of carrageenan may have a role in intestinal inflammation and possibly inflammatory bowel disease, since BCL10 resembles [[NOD2]], mutations of which are associated with genetic proclivity to [[Crohn's Disease]].
== See also ==
* [[Agar]]
* [[List of food additives]]
== References ==
{{reflist}}
{{wiktionarypar|carrageenan}}
[[Category:Edible thickening agents]]
[[Category:Polysaccharides]]
[[Category:Food additives]]
[[Category:IARC Group 2B carcinogens]]
[[Category:Personal lubricants]]
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