E407

Carrageenans or carrageenins ( ; ) are a family of natural linear sulfated polysaccharides that are extracted from 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 tissue engineering and regenerative medicine applications as they resemble native glycosaminoglycans (GAGs). They have been mainly used for tissue engineering, wound coverage and drug delivery.

Carrageenans contain 15-40% ester-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.

The most well-known and most important red seaweed used for manufacturing the hydrophilic colloids to produce carrageenan is ''Chondrus crispus'' (Irish moss), which is a dark red parsley-like plant that grows attached to rocks. Gelatinous extracts of the ''Chondrus crispus'' seaweed have been used as food additives since approximately the fifteenth century. Carrageenan is a vegetarian and vegan alternative to gelatin in some applications, so may be used to replace gelatin in confectionery and other food. There is no clinical evidence for carrageenan as an unsafe food ingredient, mainly because its fate after digestion is inadequately determined.

The first industrial scale commercial cultivation of ''Eucheuma'' and ''Kappaphycus'' spp. for carrageenan was developed in the Philippines. The global top producers of carrageenan are the Philippines and Indonesia. Carrageenan, along with agar, are used to produce traditional jelly desserts in the Philippines called ''gulaman''.

Properties

Carrageenans are large, highly flexible molecules that form curling 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.

All carrageenans are high-molecular-weight polysaccharides and mainly made up of alternating 3-linked b-D-galac- topyranose (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.

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 ''Kappaphycus alvarezii''.
* Iota forms soft gels in the presence of calcium ions. It is produced mainly from ''Eucheuma denticulatum''.
* 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 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 during their developmental history. For instance, the genus '' Gigartina'' produces mainly kappa carrageenans during its gametophytic stage, and lambda carrageenans during its 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 EU additive E numbers E407 or E407a when present as "processed eucheuma seaweed". Technically carrageenan is considered a dietary fibre.http://www.marine-science.co.jp/english/goods/carra.html , Marine Science Co. Ltd.

In parts of Scotland and Ireland, where it is known by a variety of local and native names, ''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, tapioca, or blancmange.

Production

Although carrageenans were introduced on an industrial scale in the 1930s, they were known to be used in China since around 600 BCE (where ''Gigartina'' was used) and in Ireland around 400 CE Carrageen 'gelatin' can be prepared by boiling of rinsed Irish moss in of water for 10 minutes, stirring the mixture as it boils. of cold water are rapidly added to the hot brew and, after the mixture has cooled, it is strained through a cloth. It is then cooled for 24 hours, during which time it becomes gelatinous.

, global sales of carrageenan were estimated at $640 million. The largest producer of industrial carrageenan was the Philippines, where cultivated seaweed produces about 80% of the world supply, while China is the main exporter to global markets in the US and Europe. The most commonly used sources are '' E. cottonii'' (''Kappaphycus alvarezii'', '' K. striatum'') and '' E. spinosum'' (''Eucheuma denticulatum''), which together provide about three-quarters of the world production. These grow from the sea surface to a depth of about . 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 .

The ''E. cottonii'' variety has been reclassified as ''Kappaphycus cottonii'' by Maxwell Doty (1988), thereby introducing the genus ''Kappaphycus'', on the basis of the phycocolloid

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