Structure evolution during gelation at later stages of spinodal decomposition in gelatin/maltodextrin mixtures

The kinetics of phase separation and gelation in kinetically trapped gelati n/maltodextrin/water gels was studied using confocal laser scanning microsc opy (CLSM) and transmission electron microscopy (TEM). The time evolution o f the morphology was followed by CLSM during temperature quenches from 60 d egreesC to between 1 and 40 degreesC. The maltodextrin concentration was va ried between 2.25% and 7.5% (w/w), and the gelatin concentration was held c onstant at 4% (w/w). Spinodal decomposition, self-similar growth, percolati on-to-cluster transition, coalescence, and diffusion of maltodextrin inclus ions were observed during the progress of gelation. The start and completio n of these processes, the onset of phase separation, and the relative rates of phase separation and gelation were found to determine the morphology. T he characteristic wavelength showed a crossover in its growth rate power la w from one-third to one in a slowly gelling, near-symmetric system. Droplet and bicontinuous morphologies were observed in off-symmetric and near-symm etric quenches, respectively. Secondary phase separation occurred at low te mperatures and near-symmetric composition. Partial coalescence and contract ed flocculation were observed during the progress of gelation. Stereologica l measurements showed that the size of maltodextrin inclusions increases an d that the volume fraction decreases with increasing quench temperature. In addition, the number of the maltodextrin inclusions decreases with increas ing quench temperature.