2.2.3.3 Carrageenan
Synonyms Irish moss; Chondrus.
Biological Source Carrageenan refers to closely associated hydrocolloids which are obtained from different red algae or seaweeds. The most important sources of carrageenan are namely: Chondrus crispus (Linn.) stockhouse and Gigartina mamillosa (Goodnough and Woodward) J. Agardh belonging to the family Gigartinaceae).
Geographical Source The plants are abundantly found along the north-western coast of France, the coast of Nova Scotia, and the British Isles.
Preparation In general, the plants are collected mostly during June and July, and spread out on the bench for natural drying. They are then exposed to the sun rays directly whereby bleaching takes place. Now, they are treated with a brine solution, and ultimately dried and stored.
Description The Chondrus is more or less an allusion to the cartilage-like characteristic features of the dry thallus; whereas Gigartina is an absolute allusion specifically to the fruit bodies which appear as raised tubercles on the thallus.
Chemical Constituents The carrageenan bears a close physical resemblance to agar. However, its hydrocolloids are mostly galactans having sulphate esters, which are present in excess amount in comparison to agar. Carrageenan polysaccharides essentially comprise of chains of 1, 3 linked β – (+) – galactose and 1,4-linked α- (+) – galactose moieties that are invariably substituted and later on
modified to the 3, 6- anhydro derivative. In fact, carrageenans may be further separated into three major components, namely: k-carrageenan; i-carrageenan; and λ carrageenan.
Uses
1. Both k-and i-carrageenans proved to be good gelating agents because of the fact that they tend to orient in stable helics when in solution.
2. The λ-carrageenan does not form stable helics and hence represent the nongelling portion of the carrageenans which serves as a more useful thickner.
3. The fairly stable texture and supported by excellent rinsability of the hydrocolloids these are immensely useful in the formulations of toothpastes.
4. They are used as bulk laxative.
5. They are employed as a demulscent.
6. They constitute as an important ingredient in a large number of food preparations.
