Gelation and phase separation in maltodextrin-caseinate systems

A range of rheological techniques, including small deformation isothermal runs following quenching, controlled rate heating profiles, mechanical spectra, and large deformation strain sweeps and creep compliance testing, were employed in the investigation of maltodextrin—sodium caseinate aqueous dispersions. The concentration dependence, viscoelastic ratio and melting profiles of shear moduli for concentrated maltodextrin samples suggest a highly aggregated, enthalpically linked biopolymer gel. By contrast, the caScinate particles form a ‘pasty’ solid at low temperatures with a high viscous component, which upon moderate heating reverts readily into an entropically driven liquid body. Mixing of the polymers results in a composite system whose phase inversion from a maltodextrin continuous network with discontinuous protein inclusions to a caScinate dispersion suspending the polysaccharide particles is determined by the weight ratio of the two components in the blend. The overall strength of the composite has been related to the mechanical functions of the individual components, and the idea of kinetically trapped mixed gels has been put forward to rationalize the solvent partition between the two constituent phases. Results were used to advance the conclusions reached from work on other mixed biopolymer systems carried out in this laboratory.