Thermoreversible gelation and viscoelasticity of κ-carrageenan hydrogels

Abstract

The gelation behavior of κ-carrageenan in aqueous solution was studied by microdifferential scanning calorimetry and rheology. It was found that the formation and melting of κ-carrageenan hydrogels were thermally reversible and extremely sensitive to κ-carrageenan concentration. In comparison with the crossover of G′ and G″, the extrapolation method based on multiwave oscillation and Winter–Chambon criterion were able to give more accurate critical gel temperature Tc. At the gel point, the critical relaxation exponent n was almost constant whereas the critical gel strength Sg increased with κ-carrageenan concentration. In the stable gel state, the plateau modulus Ge depended on temperature according to a power-law scaling, Ge ∝ ε2.2, where ε is the relative distance (=|T − Tc|/Tc) and independent of κ-carrageenan concentration. The presence of potassium ions shifted the formation and melting temperatures of κ-carrageenan hydrogel to higher temperatures, and the temperatures for gel formation and melting increased with increasing potassium ions' content.