Viscoelastic properties of cross-linked waxy cornstarch and κ-carrageenan mixtures under a wide range of potassium counter-ion concentrations

The small-deformation shear behavior at 25 °C of 1%-4%(mass fraction) cross-linked waxy corn starch (CWCS) and 0.5%(mass fraction) κC mixtures with and without KCl were studied. Dispersions were heated (1.5 °C/min) to 90 °C, held for 10 min, then cooled (1.5 °C/min) to 90 °C. When the volume fraction of CWCS is about 0.5 to 0.7, the rheological behavior is governed by the continuous phase, while above these values the disperse phase dominates the rheological behavior. When carrageenan is in a disordered state without KCl, the swollen granules are dispersed in a macromolecular solution. With KCl, the rigidity of the gels increases by effect of CWCS, carrageenan and salt concentrations. However, salt concentrations above 100 mmol/L lead to a marginal increase in rigidity. Results can be interpreted in terms of two types of systems: particles suspended in a macromolecular solution and composite gels of particles embedded in a network matrix when both κC and KCl were added.