Carrageenans: Structure, Properties and Applications

Carrageenans were first extracted in 1837 from seaweeds, and thereafter, the process of extraction continuously taking place mainly from the Rhodophyceae family. Carrageenans are natural marine-based seaweed (Rhodophyceae)-derived polysaccharides. They are mainly composed of D-galactose and 3,6-anhydro-D-galactose sugar units with sulphate as the main substituent, along with some methyl ethers. They have been widely utilised in the food industry mainly as gelling, thickening, stabilising and protein-binding agents. The pharmaceutical applications include drug delivery devices, matric and excipients. The chapter highlights the important aspects of carrageenans related to their extraction, structure, properties and applications in various fields. Carrageenans are linear anionic sulphated polysaccharides present as a matrix material in seaweeds, serving a structural function analogous to cellulose in land plants. Polysaccharides can be obtained from a number of sources, including plants, animals, microbes, seaweeds, crustaceans and insects. Natural polysaccharides are being extensively utilised in drug delivery systems due to their biocompatibility, toxicological harmlessness, biodegradability and sustainable properties.