Time-resolved small angle x-ray scattering and dynamic light scattering studies of sol-gel transition in gelatin

The authors describe structural and dynamic properties of an aqueous gelatin solution in a sol-gel transition studied by time-resolved small angle x-ray scattering (SAXS) and dynamic light scattering (DLS) after quenching the gelatin sol. SAXS intensity measurements suggested the presence of gel fibrils which grew initially in cross-section. The average cross-section of the gel fibrils reached a constant value after an initial growth period of 800 sec. Further increase in SAXS intensity could be attributed to the increase in the length of the gel fibrils. Photo correlation, on the other hand, clearly showed two relaxation modes on both the sol and the gel states: a fast cooperative diffusion mode which remained constant from the sol to the gel state after correction for the temperature dependence of the solvent viscosity; and a slow mode that could be attributed to the self-diffusion of the free gelatin chains and aggregates