Behavior of kappa-carrageenan in glycerol and sorbitol solutions

The solubility of kappa-carrageenan in low water-content solvents is important in food applications where complete solubilization is required for proper development of structure and rheology. The effect of glycerol and sorbitol on the gelation and conformational helix transition of kappa-carrageenan was studied using rheology and optical rotation. Glycerol/water solutions from 0¯100 wt% glycerol and sorbitol solutions from 0¯100% saturation were studied over the temperature range 0¯90°C. The results were analyzed in terms of solvent solubility parameters, water chemical potential, and solvent dielectric constant. Effective cohesive energy density parameters could not be inferred for the carrageenan, but the gelation temperature could be correlated with solvent dielectric constant. Hydrogen bonding interactions control the carrageenan helix formation. The cohesive energy density as a measure of solvent quality accounts for hydrogen bonding but not Coulombic interactions, and the Coulombic interactions scale on dielectric constant. This indicates the dominant role of electrostatics on the gelation process.