Structural studies on matrices of deacylated gellan with polydextrose

The effect of varying concentrations of co-solute (polydextrose) on thermomechanical and physicochemical properties of deacylated gellan matrices is presented. Modulated differential scanning calorimetry, micro differential scanning calorimetry, small deformation dynamic oscillation in shear, Fourier transform infrared spectroscopy, wide angle X-ray diffraction and environmental scanning electron microscopy have been used to investigate the structural transformations in aqueous, low-solid and condensed systems. There was a rise in values of storage modulus as the level of co-solute was increased, followed by a significant decline at intermediate concentrations, with high modulus values being regained as more of the co-solute was incorporated. These results confirm the hypothesis of a structural transformation from a highly enthalpic aggregated assembly in the aqueous/low-solid environment to a lightly cross linked polysaccharide network in the high solids regime. Time–temperature superposition (TTS) phenomena observed for amorphous synthetic polymers have been utilised to generate master curves of viscoelasticity, which afforded rationalisation of results on the basis of the free volume theory.

► We present thermomechanical and physicochemical characteristics of gellan/polydextrose systems.
► Gellan forms a continuous matrix with enhanced structural cohesion and thermal stability.
► High solid preparations of gellan/polydextrose undergo a rubber-to-glass transition upon cooling.