Phase behavior of the ι-Carrageenan/Maltodextrin/water system at different potassium chloride concentrations and temperatures

Equilibrium phase diagrams of the ι-carrageenan/maltodextrin/water system have been established at potassium chloride (KCl) concentrations of 0.1, 0.2, and 0.3 M and 80, 85 and 90°C. All pseudo-binary phase diagrams of ι-carrageenan/maltodextrin mixtures suggested classic segregative phase separation. The binodal was heavily skewed toward the maltodextrin axis. The high asymmetry of the ι-carrageenan/maltodextrin/water phase diagram determined by the phase-volume-ratio method was consistent with the compositional analysis of phase-separated ι-carrageenan/maltodextrin samples and can be explained in terms of the Flory-Huggins interaction parameter, reflecting a higher water-binding ability of the charged ι-carrageenan than neutral maltodextrin. Increasing the concentration of ι-carrageenan-gel-promoting KCl from 0.1 to 0.3 M at 80°C enlarged the two-phase domain, whereas increasing temperature from 80 to 90°C at 0.3 M KCl enhanced biopolymer compatibility. The effects of salt concentration and temperature have been related to the differences in the Flory-Huggins interaction parameters of the two biopolymers with water as well as the helix formation of ι-carrageenan in the presence of KCl through the changes in the slopes of tie lines of phase-separated samples.