Carrageenans: Natural Polymers present in Seaweeds

Carrageenan found in red algae is a water-soluble anionic polysaccharide containing sulphated groups. Carrageenans are classified as &kappa-carrageenan, &iota-carrageenan and &lambda-carrageenan according to their different content of sulphated groups and 3,6-anhydro-D-galactose, and their different gel-formation abilities. Carageenans have characteristic properties as follows i) stabilizing proteins through a strong interaction with them and ii) changing the gel-formation ability by the addition of cationic ions. Therefore, they are used as natural thickeners and syneresis-preventing agents in the field of food engineering.^1,2) The applications to imaging phantoms,^3,4) superabsorbent polymers,^5,6) capsules^7,8) and drug delivery systems (DDS)⁹⁾ have been also reported.