Carrageenans are natural polysaccharides, present in certain varieties of red seaweeds, capable of forming viscous colloidal dispersions or gels, in aqueous and/or milk media.
Chemically, carrageenans are polygalactans, lineal polymers of alternating molecules of D-galactose and 3-6 anhydro galactose (3-6 AG), joined by alpha 1-3 and beta 1-4 links.
The galactose molecules have sulphate and/or pyruvate groups, generally found as sodium, potassium or calcium salts.
The content and position of the sulphate groups, distinguishes the four groups of commercially important carrageenans. These little variations in the chemical composition generate the differences in their functionality. However, all of them share some general characteristics:
- Produce viscosity
- Gel formation requires a proper dispersion of the carrageenan in water or milk. This is best accomplished by a heating step to achieve the “activation temperature” and total hydration of the molecules. Once hydrated the gels will stay in formation even at ambient temperatures.
- The formed gels are thermo-reversible.