Mixed iota and kappa carrageenan gels in the presence of both calcium and potassium ions

The effect was studied of adding both KCl and CaCl2 on gelation of solutions of ι-carrageenan, κ-carrageenan and mixtures of both types. The gel temperature (Tg) of ι-car was found to be determined by the CaCl2 concentration and Tg of κ-car by the KCl concentration. At a given salt concentration, ι-car was stiffest with pure CaCl2, but κ-car gels and mixed carrageenan gels were stiffer when both KCl and CaCl2 were present. Gelation of κ-car increased the turbidity of mixed carrageenan gels in the presence of KCl or CaCl2, but when both salts were present it led to a drop of the turbidity. In mixed salt, K+ induces formation of a homogeneous κ-car network that causes the mixed network to become more homogeneous. Rheological and structural properties of carrageenan gels can be tuned for a given polymer and salt concentration by adding both KCl and CaCl2 to κ-car/ι-car mixtures.