The Characteristics and Use of Carrageenans Essay

ABSTRACTIndustrially important sulphated galactans, known as carrageenans are extracted from a number of red seaweeds. Theses polysaccharides have a linear structure of alternating 3-linked--D-galactopyranose (G-units) and 4-linked--D-galactopyranose units (D-units). For food industrial application purposes, carrageenan is classified into three types as kappa (-), iota (-) and lambda (-) carrageenan according to the number (one-two and three) of sulfate groups per repeat unit of disaccharide, respectively. Under proper conditions, -carrageenan and -carrageenan in aqueous solution undergo a thermoreversible sol-gel transition, while no gelation takes place in -carrageenan having more electrolyte groups. In general terms, -carrageenan gels are hard, strong and brittle, whereas -carrageenan forms soft and weak gels. Carrageenans are used as thickeners, stabilizers and gelling agents. Therefore, they are widely used in food formulations, the dairy sector representing the largest part and, in meat applications. INTRODUCTIONCarrageenans are a family of sulfated polysaccharides extracted from red algae. Despite their widespread application, especially in the food industry as thickening and stabilizing agents, the mechanism of gelation has been a matter of discussion over the past years and further investigation is still needed for a full comprehension of the process.The objective of this paper is to introduce the reader to some generalities of carrageenans and the latest findings regarding their mechanism of gelation. HISTORYCarrageenan is the generic name for a family of gel-forming, viscosifying, sulfate polysaccharides that are obtained commercially by alkali extraction of certain species of red seaweeds (Rhodophyceae). The main species responsible for most of today's carrageenan production belong to the following genera Gigartina (ArgentinaChile, France, Morocco), Chondrus (France, North Atlantic), Iridaea (Chile), and Eucheuma (PhilippinesIndonesia) (Van de Velde et al, 2002).For several hundred years, carrageenan has been used as a thickening and stabilizing agent in food, in Europe and the Far East. In Europe the use of carrageenan started more than 600 years ago in Ireland. In the village of Carraghen on the south Irish coast, flans were made by cooking the so-called Irish moss...

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