Mechanism and kinetics of phase separation in a gelatin/maltodextrin mixture studied by small-angle light scattering.

Abstract

Phase separation mechanisms and kinetics were studied using small-angle light scattering in a gelatin/maltodextrin system where phase separation could be studied in both liquid and gelled states. Nucleation and growth or spinodal decomposition occurred, depending on the quench depth. The transition between the two mechanisms occurred relatively sharply. The different mechanisms were distinguishable by the different behavior of the scattering function even though a peak was observed in both cases. Particular differences were the different evolution of the peak intensity and position, the absence of dynamic scaling of the nucleation and growth scattering function, and the final coarsening exponent of 1/3 that was measured when spinodal decomposition occurred but not for nucleation and growth. Gelation severely reduced the coarsening rate and initially placed the phase compositions far from their equilibrium values. Despite the loss of molecular mobility caused by gelation, the gelled systems did continue to evolve, albeit much more slowly than in the liquid case. Multiple coarsening rates were observed for some of the gelled samples, which were ascribed to the gradual movement of these systems toward the equilibrium compositions.