View source for Chemistry:Carrageenan

{{Short description|Natural linear sulfated polysaccharide}}
[[File:Eucheuma farming, Philippines (5211726476).jpg|thumb|Underwater ''Eucheuma'' farming in the {{wipe|Philippines}} for carrageenan production]]
'''Carrageenans''' or '''carrageenins''' ({{IPAc-en|ˌ|k|ær|ə|ˈ|ɡ|iː|n|ə|n|z}} {{respell|KARR|ə|GHEE|nənz}}; {{etymology|ga|{{wikt-lang|ga|carraigín}}|little rock}}) are a family of natural linear [[Biology:Sulfation|sulfated]] [[Chemistry:Polysaccharide|polysaccharide]]s that are extracted from [[Biology:Red algae|red]] edible seaweeds. Carrageenans are widely used in the food industry, for their gelling, thickening, and stabilizing properties. Their main application is in dairy and meat products, due to their strong binding to food proteins. In recent years, carrageenans have emerged as a promising candidate in [[Engineering:Tissue engineering|tissue engineering]] and regenerative medicine applications as they resemble native [[Chemistry:Glycosaminoglycan|glycosaminoglycan]]s (GAGs). They have been mainly used for tissue engineering, wound coverage, and drug delivery.<ref>{{Cite journal|last1=Yegappan|first1=Ramanathan|last2=Selvaprithiviraj|first2=Vignesh|last3=Amirthalingam|first3=Sivashanmugam|last4=Jayakumar|first4=R.|date=October 2018|title=Carrageenan based hydrogels for drug delivery, tissue engineering and wound healing|url=https://linkinghub.elsevier.com/retrieve/pii/S0144861718307410|journal=Carbohydrate Polymers|language=en|volume=198|pages=385–400|doi=10.1016/j.carbpol.2018.06.086|pmid=30093014|s2cid=51953085}}</ref> 

Carrageenans contain 15–40% [[Chemistry:Ester|ester]]-[[Chemistry:Sulfate|sulfate]] content, which makes them anionic polysaccharides. They can be mainly categorized into three different classes based on their sulfate content. Kappa-carrageenan has one sulfate group per disaccharide, iota-carrageenan has two, and lambda-carrageenan has three.<ref>{{Citation |last=Tuvikene |first=R. |title=Carrageenans |date=2021 |url=https://doi.org/10.1016/B978-0-12-820104-6.00006-1 |work=Handbook of Hydrocolloids (Third Edition) |pages=767–804 |editor-last=Phillips |editor-first=Glyn O. |access-date= |series= |publisher=Elsevier |doi=10.1016/b978-0-12-820104-6.00006-1 |isbn=978-0-12-820104-6 |editor2-last=Williams |editor2-first=Peter A.}}</ref>

A common red seaweed used for manufacturing the [[Chemistry:Hydrophilic|hydrophilic]] colloids to produce carrageenan is ''[[Biology:Chondrus crispus|Chondrus crispus]]'' (Irish moss), which is a dark red parsley-like alga that grows attached to rocks. Gelatinous extracts of the ''Chondrus crispus'' seaweed have been used as food additives since approximately the fifteenth century.<ref>[http://www.fao.org/docrep/field/003/AB730E/AB730E03.htm FAO Agar and Carrageenan Manual]. Food and Agriculture Organization of the United Nations (1965-01-01). Retrieved on 2011-12-10.</ref> Carrageenan is a [[Philosophy:Vegetarianism|vegetarian]] and [[Philosophy:Veganism|vegan]] alternative to [[Biology:Gelatin|gelatin]] in some applications, so may be used to replace gelatin in confectionery and other food. There is no [[Medicine:Evidence-based medicine|clinical evidence]] for carrageenan as an unsafe food ingredient, mainly because its fate after digestion is inadequately determined.<ref name=efsa/>

The first industrial scale [[Biology:Seaweed farming|commercial cultivation]] of ''[[Biology:Eucheuma|Eucheuma]]'' and ''[[Biology:Kappaphycus|Kappaphycus]]'' spp. for carrageenan was developed in the {{wipe|Philippines}}. The global top producers of carrageenan are the Philippines and Indonesia.<ref name="Buschmann">{{cite journal |last1=Buschmann |first1=Alejandro H. |last2=Camus |first2=Carolina |last3=Infante |first3=Javier |last4=Neori |first4=Amir |last5=Israel |first5=Álvaro |last6=Hernández-González |first6=María C. |last7=Pereda |first7=Sandra V. |last8=Gomez-Pinchetti |first8=Juan Luis |last9=Golberg |first9=Alexander |last10=Tadmor-Shalev |first10=Niva |last11=Critchley |first11=Alan T.|display-authors=3 |title=Seaweed production: overview of the global state of exploitation, farming and emerging research activity |journal=European Journal of Phycology |date=2 October 2017 |volume=52 |issue=4 |pages=391–406 |doi=10.1080/09670262.2017.1365175 |s2cid=53640917 |language=en |issn=0967-0262}}</ref><ref name="PEMSEA">{{cite book |title=Impact Investment for a Business Venture for Community-Based Seaweed Farming in Northern Palawan, Philippines |date=2017 |publisher=Blue Economy Impact Investment East Asia & Partnerships in Environmental Management for the Seas of East Asia |url=http://seaknowledgebank.net/sites/default/files/Business%20Concept%20Community-based%20Seaweed%20Farming%20Philippines%20-%20FINAL_0.pdf |access-date=8 February 2021}}</ref><ref name="Habito">{{cite news |last1=Habito |first1=Cielito F. |title=Sustaining seaweeds |url=https://opinion.inquirer.net/16365/sustaining-seaweeds |access-date=8 February 2021 |newspaper=Philippine Daily Inquirer |date=1 November 2011}}</ref> Carrageenan, along with [[Biology:Agar|agar]], are used to produce traditional jelly desserts in the {{wipe|Philippines}} called ''[[Chemistry:Gulaman|gulaman]]''.<ref name="Montaño">{{cite news |last1=Montaño |first1=Marco Nemesio |title=Gelatin, gulaman, 'JellyAce,' atbp. |url=https://www.philstar.com/business/science-and-environment/2004/09/16/264974/gelatin-gulaman-145jellyace146-atbp |access-date=10 February 2021 |work=PhilStar Global |date=16 September 2004}}</ref>

== Properties ==
[[File:Moleculare structure of different carrageenan types.svg|thumb|310px|The molecular structures of different types of carrageenan]]

Carrageenans are large, highly flexible molecules that form curling [[Helix|helical]] structures. This gives them the ability to form a variety of different [[Physics:Gel|gel]]s at room temperature. They are widely used in the food and other industries as [[Chemistry:Thickening agent|thickening]] and [[Chemistry:Stabilizer|stabilizing agents]].

All carrageenans are high-molecular-weight polysaccharides and mainly made up of alternating 3-linked b-D-galactopyranose (G-units) and 4-linked a-D-galactopyranose (D-units) or 4-linked 3,6-anhydro-a-D-galactopyranose (DA-units), forming the disaccharide repeating unit of carrageenans.<ref>{{Cite journal|last1=Campo|first1=Vanessa Leiria|last2=Kawano|first2=Daniel Fábio|last3=Silva|first3=Dílson Braz da|last4=Carvalho|first4=Ivone|date=2009-06-10|title=Carrageenans: Biological properties, chemical modifications and structural analysis – A review|url=https://www.sciencedirect.com/science/article/pii/S0144861709000459|journal=Carbohydrate Polymers|language=en|volume=77|issue=2|pages=167–180|doi=10.1016/j.carbpol.2009.01.020|issn=0144-8617}}</ref>

There are three main commercial classes of carrageenan:

* ''Kappa'' forms strong, rigid gels in the presence of potassium ions, and reacts with dairy proteins. It is sourced mainly from ''[[Biology:Kappaphycus alvarezii|Kappaphycus alvarezii]]''.<ref name=":1">{{Cite web|url=http://www.fao.org/docrep/006/y4765e/y4765e00.htm#Contents|title=A guide to the seaweed industry: FAO Fisheries Technical Paper 441|last=McHugh|first=Dennis J.|date=2003|website=www.fao.org|publisher=Food and Agriculture Organization of the United Nations|access-date=2017-07-29}}</ref>
* ''Iota'' forms soft gels in the presence of calcium ions. It is produced mainly from ''[[Biology:Eucheuma denticulatum|Eucheuma denticulatum]]''.<ref name=":1" />
* ''Lambda'' does not gel, and is used to thicken dairy products.

The primary differences that influence the properties of kappa, iota, and lambda carrageenan are the number and position of the ester sulfate groups on the repeating [[Chemistry:Galactose|galactose]] units. Higher levels of ester sulfate lower the solubility temperature of the carrageenan and produce lower strength gels, or contribute to gel inhibition (lambda carrageenan).

Many red algal species produce different types of carrageenans [[Biology:Alternation of generations|during their developmental history]]. For instance, the genus ''Gigartina'' produces mainly kappa carrageenans during its [[Biology:Gametophyte|gametophytic]] stage, and lambda carrageenans during its [[Biology:Sporophyte|sporophytic]] stage. 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 [[Social:European Union|EU]] additive [[Chemistry:E number|E number]]s E407 or E407a when present as "processed eucheuma seaweed".<ref name="FSA" /> Technically carrageenan is considered a dietary fibre.<ref name="Marine Science Co. Ltd. Japan">http://www.marine-science.co.jp/english/goods/carra.html {{Webarchive|url=https://web.archive.org/web/20181103072527/http://www.marine-science.co.jp/english/goods/carra.html |date=2018-11-03 }}, Marine Science Co. Ltd.</ref><ref name="Vegetarian Times April 1993">{{Cite journal|url = https://books.google.com/books?id=hQgAAAAAMBAJ|title = Answering Machine: Carra-what?|last = DeSilver|first = Drew|date = April 1993|journal = Vegetarian Times|access-date = 12 August 2014|page = 28}}</ref>

In parts of Scotland and Ireland, where it is known by [[Biology:Chondrus crispus#Names in various languages|a variety of local and native names]], ''[[Biology:Chondrus crispus|Chondrus crispus]]'' is boiled in milk and strained, before sugar and other flavourings such as vanilla, cinnamon, brandy, or whisky are added. The end-product is a kind of jelly similar to panna cotta, [[Biology:Tapioca|tapioca]], or blancmange.

== Production ==
{{more citations|section|date=October 2023}}
[[File:Eucheuma denticulatum in an off-bottom cultivation, Bweleo, Zanzibar.JPG|thumb|''Eucheuma denticulatum'' being farmed for iota-carrageenan in an off-bottom cultivation in Tanzania]]
Although carrageenans were introduced on an industrial scale in the 1930s, they were known to be used in {{wipe|China}} since around 600&nbsp;BCE (where ''Gigartina'' was used) and in Ireland around 400&nbsp;CE<ref>{{cite book|last1=Loureiro|first1=Rafael R.|last2=Cornish|first2=M.L.|last3=Neish|first3=Iain C.|editor1-last=Hurtado|editor1-first=Anicia Q.|editor2-last=Critchley|editor2-first=Alan T.|editor3-last=Neish|editor3-first=Iain C.|title=Tropical Seaweed Farming Trends, Problems and Opportunities: … |date=2017|publisher=Springer International Publishing|location=Berlin, Germany|page=165|chapter-url=https://books.google.com/books?id=yH86DwAAQBAJ&pg=PA165|chapter=Applications of carrageenan: With special reference to iota and kappa forms as derived from the Eucheumatoid seaweeds|isbn=9783319634982}}</ref><ref>{{cite journal |last1=Mitchell |first1=M.E. |last2=Guiry |first2=M.D. |title=Carrageen: A local habitation or a name? |journal=Journal of Ethnopharmacology |date=December 1983 |volume=9 |issue=2–3 |pages=347–351 |doi=10.1016/0378-8741(83)90043-0 |pmid=6677826 }}</ref> 

Carrageenan derived from ''[[Biology:Eucheuma|Eucheuma]]'' spp. (today one of the main cultivated sources of carrageenan), known as ''gusô'' or ''tambalang'' in the Visayan languages, has also been traditionally used as food in the {{wipe|Philippines}}. They were first recorded in the ''Diccionario De La Lengua Bisaya, Hiligueina y Haraia de la isla de Panay y Sugbu y para las demas islas'' (c.1637) of the Augustinian missionary Alonso de Méntrida {{In lang|es}}. In the book, Méntrida describes gusô as being cooked until it melts, and then allowed to congeal into a sour dish.<ref>{{cite book |last1=de Mentrida |first1=Alonso |title=Diccionario De La Lengua Bisaya, Hiligueina Y Haraya de la isla de Panay |date=1841 |publisher=En La Imprenta De D. Manuel Y De D. Felis Dayot |page=380}}</ref>

The most commonly used sources are ''Eucheuma cottonii'', ''Kappaphycus alvarezii'',  and ''Eucheuma spinosum'', which together provide about three-quarters of the world production.{{cn|date=October 2023}} These grow from the sea surface to a depth of about {{cvt|2|m|ft}}. The seaweed is normally grown on nylon lines strung between bamboo floats, and it is harvested after three months or so, when each plant weighs approximately {{cvt|1|kg|lb|abbr=on}}.

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 [[Chemistry:Alkali|alkali]] solution (e.g., 5–8% [[Chemistry:Potassium hydroxide|potassium hydroxide]]), the [[Chemistry:Cellulose|cellulose]] is removed from the carrageenan by centrifugation and [[Chemistry:Filtration|filtration]]. The resulting carrageenan solution is then concentrated by [[Physics:Evaporation|evaporation]]. It is dried and ground to specification.

There are three types of industrial processing:

===Semi-refined===

This is only produced from ''E. cottonii'' or ''E. spinosum''. The raw weed is first sorted and crude contaminants are removed by hand. The weed is then washed to remove salt and sand, and then cooked in hot alkali to increase the gel strength. The cooked weed is washed, dried, and milled. ''E. spinosum'' undergoes a much milder cooking cycle, as it dissolves quite readily. The product is called semi-refined carrageenan, Philippines natural grade, or, in the U.S., it simply falls under the common carrageenan specification.<ref>CyberColloids: [http://www.cybercolloids.net/library/euspecs/e-407-carrageenan E407 Specification Carrageenan], CyberColloids, Hydrocolloids research and development webpage.</ref>

                            cleaned and washed seaweed 
                                    ↓
                                 extraction
                                    ↓
                              coarse filtration   → seaweed residue
                                    ↓ 
                               fine filtration    → used filter aids
                                    ↓
             ↓-------------- concentration --------------↓
    preparation with KCl                        preparation with alcohol
             ↓                                           ↓
        gel pressing                                alcohol recovery 
             ↓                                           ↓
          drying                                      drying
             ↓                                           ↓ 
          milling                                     milling 
             ↓                                           ↓ 
          blending                                    blending
             ↓                                           ↓
     gel refined carrageenan                     refined carrageenan

===Refined===
The essential difference in the refining process is that the carrageenan is first dissolved and filtered to remove cell wall debris. The carrageenan is then precipitated from the clear solution, either by isopropyl alcohol (propan-2-ol) or by potassium chloride.<ref>CyberColloids: [http://www.cybercolloids.net/library/euspecs/e-407a-processed-eucheuma-seaweed E407a Specification Processed Eucheuma Seaweed], Hydrocolloids research and development webpage.</ref>

===Mixed processing===
A hybrid technology in which seaweed is treated heterogeneously as in the semirefined process exists, but alcohol or high salt levels are used to inhibit dissolution. This process is often used on South American seaweeds and gives some of the cost benefits of semirefined processing, while allowing a wider range of seaweeds to be processed, however, the naturally low cellulose levels in some South American seaweeds allow them to be heterogeneously processed and still be sold under the EU refined specification.

=== Grades ===
There are two basic grades of carrageenan, refined (RC) and semi-refined (SRC). In the United States, both grades are labeled as carrageenan. In the European Union, refined carrageenan is designated by the [[Chemistry:E number|E number]] E-407 and semi-refined carrageenan as E-407a.<ref name=FSA>{{cite web|url=http://www.food.gov.uk/safereating/chemsafe/additivesbranch/enumberlist#h_6 |title=Current EU approved additives and their E Numbers |publisher=Food Standards Agency |date=26 November 2010 |access-date=12 August 2014}}</ref> Refined carrageenan has a 2% maximum for acid-insoluble material and is produced by alcohol precipitation or potassium chloride gel press process. Semi-refined carrageenan has a much higher cellulose content and is produced in a less complex process. Indonesia, the Philippines, and Chile are three main sources of raw material and extracted carrageenan.

== Uses and applications ==
{{more citations|section|date=October 2023}}
===Food and other domestic uses===
* Desserts, [[Engineering:Ice cream|ice cream]], cream, milkshakes, yogurts, salad dressings, sweetened condensed milks
* Sauces: to increase viscosity
* Beer: clarifier to remove haze-causing proteins
* Pâtés and processed meats (e.g., ham): substitute for fat, increase water retention, increase volume, or improve slicing
* [[Medicine:Toothpaste|Toothpaste]]: stabilizer to prevent constituents separating

* Fire fighting foam: thickener to cause foam to become sticky
* [[Medicine:Shampoo|Shampoo]] and cosmetic creams: thickener
* Air freshener gels
* Marbling: the ancient art of paper and fabric marbling uses a carrageenan mixture on which to float paints or inks; the paper or fabric is then laid on it, absorbing the colours
* Shoe polish: to increase [[Physics:Viscosity|viscosity]]
* [[Engineering:Biotechnology|Biotechnology]]: to immobilize cells and enzymes
* Pharmaceuticals: used as an inactive [[Chemistry:Excipient|excipient]] in pills and tablets
* Soy milk and other plant milks: to thicken
* Diet sodas: to enhance texture and suspend flavours
* Pet food
* Personal lubricants
* Vegetarian hot dogs

===Regulatory status===

In the U.S., carrageenan is allowed under FDA regulations<ref>21 Code of Federal Regulations 172.620</ref> as a direct food additive and is considered [[Chemistry:Generally recognized as safe|safe]]<ref>Generally Recognized As Safe 21 CRF §182.7255 GRAS ID Code 9000-07-1 (1973)</ref> when used in the amount necessary as an emulsifier, stabilizer, or thickener in foods, except those standardized foods that do not provide for such use. FDA also reviewed carrageenan safety for infant formula.<ref>Federal Food, Drug, and Cosmetic Act 21 U.S.C. 350(a) §412</ref> The European Food Safety Authority concluded "there is no evidence of any adverse effects in humans from exposure to food-grade carrageenan, or that exposure to [[Chemistry:Poligeenan|degraded carrageenan]] from use of food-grade carrageenan is occurring",<ref>Opinion of the Scientific Committee on Food on Carrageenan (2003) [http://ec.europa.eu/food/fs/sc/scf/out164_en.pdf] p. 5</ref> Furthermore, the Joint FAO/WHO expert committee on food additives stated in a July 2014 review of carrageenan "that the use of carrageenan in infant formula or formula for special medical purposes at concentrations up to 1000 mg/L is not of concern".<ref>[http://www.fao.org/fileadmin/user_upload/agns/news_events/JECFA%2079%20Summary%20Version%20Final.pdf Joint FAO/WHO Expert Committee on Food Additives]. Who.int. Retrieved on 2014-8-11.</ref>

Although the National Organic Program (NOP) had added carrageenan to its National List of additives allowed to be included in organic foods in 2003,<ref>68 FR 61993 (2003)</ref> and reviewed and reauthorized it in 2008,<ref>65 FR 80548</ref> noting it as "critical to organic production and handling operations",<ref>73 FR 59481</ref> on November 18, 2016, the NOP's National Organic Standards Board (NOSB) voted to recommend carrageenan be removed from the National List of additives allowed in organic food production.<ref>{{cite web|url=https://www.ams.usda.gov/sites/default/files/media/HS2018SunsetReviews.pdf|title=Sunset 2018 Review Summary NOSB Final Review|date=2016-11-30|publisher=USDA Agricultural Marketing Service|access-date=2017-02-15}}</ref>

On April 4, 2018, the [[Organization:Agricultural Marketing Service|Agricultural Marketing Service]] (AMS) (USDA) published a document to announce the renewal of carrageenan on the National List, allowing its continued use in food products. The document states,<blockquote>The NOSB recommended removing carrageenan because they determined that alternative materials, such as gellan gum, guar gum, or xanthan gum, are available for use in organic products ... AMS found sufficient evidence in public comments to the NOSB that carrageenan continues to be necessary for handling agricultural products because of the unavailability of wholly natural substitutes (§ 6517(c)(1)(ii)). Carrageenan has specific uses in an array of agricultural products, and public comments reported that potential substitutes do not adequately replicate the functions of carrageenan across the broad scope of use. Therefore, carrageenan continues to meet the OFPA criteria for inclusion on the National List.<ref>{{cite web|url=https://www.federalregister.gov/documents/2018/04/04/2018-06867/national-organic-program-usda-organic-regulations|title=83 FR 14347|date=2018-04-04|publisher=USDA Agricultural Marketing Service|access-date=2018-04-21}}</ref></blockquote>The rule went into effect May 29, 2018.

In a 2015 review, the Joint Expert Committee of the Food and Agriculture Organization of the {{wipe|United Nations}} and [[Organization:World Health Organization|World Health Organization]] on Food Additives released a technical report in 2015 on the use of carrageenan in infant formula and found that the additive was "not of concern" in infant formula as food for special medical purposes at concentrations up to 1000 milligrams per [[Litre|litre]].<ref>{{cite book |publisher=Joint Expert Committee on Food Additives, WHO Food Additive Series: 70|title=Safety Evaluation of Certain Food Additives, 3|date=2015 |hdl=10665/171781 |isbn=9789241660709}}</ref> The use of carrageenan in infant formula, organic or otherwise, is prohibited in the EU for precautionary reasons, but is permitted in other food items.<ref>{{cite web|publisher=European Commission, Scientific Committee on Food|title=Opinion of the Scientific Committee on Food on Carrageenan|date=2003|url=http://ec.europa.eu/food/fs/sc/scf/out164_en.pdf}}</ref> In 2018, the European Food Safety Authority (EFSA) reported that safety of carrageenan in food products is based on an ADI of 75&nbsp;mg/kg body weight per day.<ref name="efsa">{{cite journal |author=EFSA Panel on Food Additives and Nutrient Sources added to Food| title=Re‐evaluation of carrageenan (E 407) and processed Eucheuma seaweed (E 407a) as food additives | journal=EFSA Journal| volume=16 | issue=4 | year=2018 | pages=e05238 | issn=1831-4732 | doi=10.2903/j.efsa.2018.5238 | pmid=32625873 | pmc=7009739 | doi-access=free }}</ref>

In the UK, the Food Standards Agency issued a product recall for sweets containing carrageenan, stating that carrageenan "is not permitted as an ingredient in jelly confectionery products as it presents a choking hazard".<ref>{{Cite web | url=https://www.food.gov.uk/news-alerts/alert/fsa-prin-28-2018 | title=Tees Ltd recalls Sweetworld Yummys Jelly Cones because of a choking hazard | access-date=2018-05-17 | archive-date=2021-01-21 | archive-url=https://web.archive.org/web/20210121043310/https://www.food.gov.uk/news-alerts/alert/fsa-prin-28-2018 | url-status=dead }}</ref>

==Toxicity research==

As of 2018, carrageenan was deemed non-toxic under certain consumption levels (75&nbsp;mg/kg bw per day), although further research was recommended, mainly focused on the fate of carrageenan during and after digestion, and on any subsequent metabolites.<ref name=efsa/><ref name="David">{{cite journal | last1=David | first1=Shlomit | last2=Shani Levi | first2=Carmit | last3=Fahoum | first3=Lulu | last4=Ungar | first4=Yael | last5=Meyron-Holtz | first5=Esther G. | last6=Shpigelman | first6=Avi | last7=Lesmes | first7=Uri | title= Revisiting the carrageenan controversy: Do we really understand the digestive fate and safety of carrageenan in our foods?| journal= Food & Function| volume=9 | issue=3 | date=2018-03-01 | issn=2042-6496 | pmid=29469913 | doi=10.1039/c7fo01721a | pages=1344–1352}}</ref>

== See also ==
* [[Biology:Agar|Agar]]
* [[Chemistry:List of food additives|List of food additives]]
* [[Chemistry:Pectin|Pectin]]
* [[Chemistry:Alginic acid|Alginic acid]]

== References ==
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<ref name=r5>{{cite journal| author= Eccles R, Meier C, Jawad M, Weinmüllner R, Grassauer A, Prieschl-Grassauer E|title= Efficacy and safety of an antiviral Iota-Carrageenan nasal spray: a randomized, double-blind, placebo-controlled exploratory study in volunteers with early symptoms of the common cold|doi=10.1186/1465-9921-11-108| year= 2010| journal= Respiratory Research| volume= 11| page= 108| pmid= 20696083| pmc= 2923116}}</ref>

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== Further reading ==
* McHugh, Dennis J. FAO Fisheries Technical Paper 288''' - '''Production and Utilization of Products from Commercial Seaweeds, [http://www.fao.org/docrep/x5822e/x5822e05.htm Chapter 3 - Production, Properties and Uses of Carrageenan], Food and Agriculture Organization, Rome, 1987
* Guiry, Michael D.R. [https://web.archive.org/web/20140407080507/http://www.seaweed.ie/uses_general/carrageenans.php Carrageenans], The Seaweed Site: information on marine algae.<!-- not used
<ref name=r4>{{cite journal|doi=10.1152/ajpgi.00380.2006 | volume=292 | title=Carrageenan induces interleukin-8 production through distinct Bcl10 pathway in normal human colonic epithelial cells | year=2006 | journal=AJP: Gastrointestinal and Liver Physiology | pages=G829–G838 | last1 = Borthakur | first1 = A. | pmid=17095757}}</ref>

<ref name=r3>{{cite journal|pmid=2047576 |title= Spectrum and Possible Mechanism of Carrageenan Cytotoxicity|year=1991|last1=Aguilar-Veiga|first1=E|last2=Sierra-Paredes|first2=G|last3=Galán-Valiente|first3=J|last4=Soto-Otero|first4=R|last5=Méndez-Alvarez|first5=E|last6=Sierra-Marcuño|first6=G|volume=71|issue=3|pages=351–64|journal=Research communications in chemical pathology and pharmacology}}</ref>

<ref name=r2>{{cite journal|pmid=332622 |title=A re-evaluation of the role of macrophages in carrageenan-induced immunosuppression|year=1977| last1=Rumjanek| first1=VM| last2=Watson| first2=SR| last3=Sljivić| first3=VS| volume=33|issue=3|pages=423–432|journal=Immunology| pmc=1445637}}</ref>

<ref name=r1>{{cite journal| url=http://cancerres.aacrjournals.org/cgi/content/abstract/42/2/496|title=  Involvement of Macrophages in the Eradication of Established Metastases following Intravenous Injection of Liposomes Containing Macrophage Activators|year=1982|journal=Cancer Research |volume=42|pages= 496–501| pmid=7055801| last1=Fidler| first1=IJ| last2=Barnes| first2=Z| last3=Fogler| first3=WE| last4=Kirsh| first4=R| last5=Bugelski| first5=P| last6=Poste| first6=G| issue=2}}</ref>
-->

==External links==
*{{Curlie|Business/Food_and_Related_Products/Additives/Gums_and_Hydrocolloids/|Food Additives: Gums and Hydrocolloids}}

[[Category:Edible thickening agents]]
[[Category:Polysaccharides]]
[[Category:IARC Group 2B carcinogens]]
[[Category:Food stabilizers]]
[[Category:E-number additives]]

{{Sourceattribution|Carrageenan}}