Carrageenan

Polysaccharide found in red algae, composed of the monosaccharide galactose in compounds containing varying quantities of sulfate. Carrageenans are long, flexible chains with about 25,000 galactose molecules. Their gelation properties are dependent on the variety and their behavior is affected by the surrounding conditions of pH, ion content, and temperature. Carrageenans are so-called electrolytes, able to form gels in the presence of K⁺ and Ca⁺⁺ ions. Some can curl into helical structures that are able to link loosely together to form a network. For technical end uses there are three important carrageenans: κ-carrageenan, which forms strong, stiff gels; ι-carrageenan, which forms softer gels; λ-carrageenan, which is well suited for emulsifying proteins. Only λ-carrageenan is soluble in cold water.