Carrageenan is a natural, high molecular weight, highly sulphated linear polysaccharide extracted from the edible red algae Rhodophycea and the hydrophilic colloid Kappaphycus alvarezii. It is also extracted from Irish moss Chondrus crispus and Gigartina stellata. The basic unit of carrageenan is D-galactose and 3,6-anhydro-D-galactose. Refined sulphated carrageenan has recently been introduced commercially.

Industrially, it appears in the form of a white to yellowish water-soluble, odourless powder.

What it is used for and where

Mainly used as an emulsifying, stabilising, gelling, film-forming ingredient in foods, cosmetics and parapharmaceuticals.

Medical

Phytochemical analysis of carrageenan has shown the presence of alkaloids, saponins, steroids, gums, mucilages and carbohydrates in both native and commercial carrageenan with antioxidant activities (1).

Food

In European food additives it is labelled with the number E407 as a thickener. Used as a stabiliser, gelling agent, binder and thickener in processed meat and poultry products. It improves the freeze-thaw ratio, stability, flavour and cuttability in poultry products. 

Carrageenan has the property of maintaining the organoleptic and structural values of fat-free cheese and can replace casein in cheese imitations and stabilise the structure in cheese-like products (2).

Lightening agent in beverages. Incorporated into confectionery products such as gummy sweets, ice cream and food jelly it can replace agar, pectin and gelatine.

Safety

A rather debated ingredient in recent years by toxicology studies and chronic toxicological tests (3).

 A 2024 study warns about the risk of developing cancer with high intakes of emulsifiers, (including E440, Pectin, E471 mono- and diglycerides of fatty acids, carrageenan, E407, sodium carbonate E500) (4).  

Carrageenan studies

Typical commercial product characteristics Carrageenan

Appearance	White powder
pH	8- 11 (1% solution)
PSA	394.53000
Sulfate	15- 40%
Loss on drying	12 Max%
Viscosity (1.5%, 75°C, mPa.s )	5 min
Gel Strength (1.5% w/w, 0.2% KCl, 25°C, g/cm2)	1500 min
Transparency	75 min
Plate Count	5000cfu/g max
Total ash	15%~40%
Acid insoluble ash	1.0% Max
Acid Insoluble matter	5.0% Max
Lead	5 mg/kg Max
Arsenic	3 mg/kg Max
Mercury	1 mg/kg Max
Cadmium	1 mg/kg Max
Total Heavy Metals (as Pb)	10 mg/kg Max
Yeasts & Moulds	300 cfu/g Max
Safety

• Molecular Formula  C₂₃H₂₃Fn₄O₇Zn
• Molecular Weight   788.65
• Exact Mass    788.09900
• CAS    9000-07-1   11114-20-8
• UNII    DV181E4639
• EC Number   232-524-2
• DSSTox Substance ID  DTXSID3020255
• IUPAC  zinc;1-(5-cyanopyridin-2-yl)-3-[(1S,2S)-2-(6-fluoro-2-hydroxy-3-propanoylphenyl)cyclopropyl]urea;diacetate
• InChI=1S/C19H17FN4O3.2C2H4O2.Zn/c1-2-15(25)11-4-5-13(20)17(18(11)26)12-7-14(12)23-19(27)24-16-6-3-10(8-21)9-22-16;2*1-2(3)4;/h3-6,9,12,14,26H,2,7H2,1H3,(H2,22,23,24,27);2*1H3,(H,3,4);/q;;;+2/p-2/t12-,14+;;;/m1.../s1  
• InChl Key      UHVMMEOXYDMDKI-JKYCWFKZSA-L
• SMILES   CCC(=O)C1=C(C(=C(C=C1)F)C2CC2NC(=O)NC3=NC=C(C=C3)C#N)O.CC(=O)[O-].CC(=O)[O-].[Zn+2]
• MDL number  MFCD00081480
• PubChem Substance ID    
• FEMA   2596
• RTECS   FI0704000

Synonyms

• kappa-Carrageenan
• k-Carrageenan
• Carrageenan Kappa Refined
• Carrageenan Kappa Semi-refined

References_______________________________________________________________

(1) Suganya AM, Sanjivkumar M, Chandran MN, Palavesam A, Immanuel G. Pharmacological importance of sulphated polysaccharide carrageenan from red seaweed Kappaphycus alvarezii in comparison with commercial carrageenan. Biomed Pharmacother. 2016 Dec;84:1300-1312.

(2) Błaszak BB, Gozdecka G, Shyichuk A. Carrageenan as a functional additive in the production of cheese and cheese-like products. Acta Sci Pol Technol Aliment. 2018 Apr-Jun;17(2):107-116. doi: 10.17306/J.AFS.0550.

Abstract. Carrageenan is a well-known gelling agent used in the food industry. The present review of patent and scien- tific literature shows that carrageenan is a useful additive in the cheese production process. The gel-strength- ening properties of carrageenan are as a result of the fairly strong bonds it forms with casein macromolecules. However, carrageenan-casein interaction is dependent on pH. Different carrageenan types have different charge levels (the most charged is the helix form of lambda-carrageenan), which affects the carrageenan- casein aggregates. The correct concentration of carrageenan and temperature treatment can improve cheese yield and whey protein recovery, which is desirable for cheese producers. Even small amounts of this hydro- colloid can increase cheese firmness and maintain cheese structure after cheese curd heating. Carrageenan improves cheese structure and other properties, such as ease of grating or slicing, which are very important for customers. Some modifications to cheese composition can destroy the natural cheese structure, but the addition of carrageenan can be useful for creating modified cheese-like products with desirable attributes. Carrageenan can be a good replacement for emulsifying salts, to stabilize cheese fat without disturbing the Ca:P ratio. The replacement of emulsifying salts with carrageenan (as little as 1%) results in a homogenous cheese product. For that reason, carrageenan is a useful additive for maintaining the organoleptic and struc- tural values of fat-free cheese. Carrageenan can also stabilize the structure in cheese-like products and replace casein in cheese imitations.

(3) David S, Shani Levi C, Fahoum L, Ungar Y, Meyron-Holtz EG, Shpigelman A, Lesmes U. Revisiting the carrageenan controversy: do we really understand the digestive fate and safety of carrageenan in our foods? Food Funct. 2018 Mar 1;9(3):1344-1352. doi: 10.1039/c7fo01721a.

Abstract. Carrageenan (CGN), a family of marine polysaccharides isolated from seaweeds, has been at the heart of considerable debate in recent years. To date, CGN is generally recognized as safe based on a history of safe use, various acute toxicology studies and some recent chronic toxicology tests. This review offers readers an overview of evidence on CGN characteristics and digestive fate that highlight various gaps in our understanding. Specifically, three unresolved gaps are identified. Firstly, little information can be found on the current levels of public exposure to CGN. Secondly, the link between CGN physicochemical properties, its impact on digestive proteolysis, the colon microbiome and inflammation are yet to be fully resolved. Thirdly, scant scientific evidence exists on the differential digestive fate of CGN in the gut of liable and predisposed populations, such as elderly people or IBD patients. Altogether, revisiting the scientific evidence indicates that more research is needed to elucidate the possibility that continued exposure to increasing levels of CGN in the human diet may compromise human health and well-being.

Tobacman JK. Review of harmful gastrointestinal effects of carrageenan in animal experiments. Environ Health Perspect. 2001 Oct;109(10):983-94. doi: 10.1289/ehp.01109983.

Abstract. In this article I review the association between exposure to carrageenan and the occurrence of colonic ulcerations and gastrointestinal neoplasms in animal models. Although the International Agency for Research on Cancer in 1982 identified sufficient evidence for the carcinogenicity of degraded carrageenan in animals to regard it as posing a carcinogenic risk to humans, carrageenan is still used widely as a thickener, stabilizer, and texturizer in a variety of processed foods prevalent in the Western diet. I reviewed experimental data pertaining to carrageenan's effects with particular attention to the occurrence of ulcerations and neoplasms in association with exposure to carrageenan. In addition, I reviewed from established sources mechanisms for production of degraded carrageenan from undegraded or native carrageenan and data with regard to carrageenan intake. Review of these data demonstrated that exposure to undegraded as well as to degraded carrageenan was associated with the occurrence of intestinal ulcerations and neoplasms. This association may be attributed to contamination of undegraded carrageenan by components of low molecular weight, spontaneous metabolism of undegraded carrageenan by acid hydrolysis under conditions of normal digestion, or the interactions with intestinal bacteria. Although in 1972, the U.S. Food and Drug Administration considered restricting dietary carrageenan to an average molecular weight > 100,000, this resolution did not prevail, and no subsequent regulation has restricted use. Because of the acknowledged carcinogenic properties of degraded carrageenan in animal models and the cancer-promoting effects of undegraded carrageenan in experimental models, the widespread use of carrageenan in the Western diet should be reconsidered.

(4) Sellem, L., Srour, B., Javaux, G., Chazelas, E., Chassaing, B., Viennois, E., ... & Touvier, M. (2024). Food additive emulsifiers and cancer risk: Results from the French prospective NutriNet-Santé cohort. Plos Medicine, 21(2), e1004338.

Abstract. Emulsifiers are widely used food additives in industrially processed foods to improve texture and enhance shelf-life. Experimental research suggests deleterious effects of emulsifiers on the intestinal microbiota and the metabolome, leading to chronic inflammation and increasing susceptibility to carcinogenesis. However, human epidemiological evidence investigating their association with cancer is nonexistent. This study aimed to assess associations between food additive emulsifiers and cancer risk in a large population-based prospective cohort.