For many centuries, red seaweeds have been used for foods in the Far East and Europe. Different species of Rhodophycae contain naturally occurring polysaccharides which fill the voids within the cellulose structure of the plant. This family of polysaccharides include carrageenan, furcellaran and agar. These polymers have a backbone of galactose but differ in the proportion and location of ester sulfate groups and the proportion of 3,6- anhydrogalactose. The differences in composition and conformation produce a wide range of rheological properties which are utilised in a large number of foods.

Different carrageenans cover a wide spectrum of rheological behaviour going from a viscous thickener to thermally reversible gels which range in texture from soft and elastic to firm and brittle. Kappa carrageenan is able to interact synergistically with other gums, such as locust bean gum and konjac mannan, to modify further the gel texture. A specific interaction between kappa carrageenan and kappa casein is widely used to stabilise dairy products.

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