The rheology of K+-κ-carrageenan as a weak gel

The pure potassium form of κ-carrageenan shows rheological behaviour which is very different to that observed for the commercial (unpurified) sample. The measured rheology at 1% concentration of the purified κ-carrageenan is consistent with weak gel behaviour. The resulting weak gel has a significantly smaller linear viscoelastic region than the unpurified commercial form. Upon large deformation, the gel flows. We report results for the viscosity versus shear rate where the sheared gel demonstrates significant structural recovery with time after shearing. The effects of temperature, polymer concentration and KCl addition on the rheology of the gel have been investigated. The role of both calcium and potassium ions is discussed.