Gel point determination of gelatin hydrogels by dynamic light scattering and rheological measurements

The sol-gel transition of gelatin aqueous solutions has been investigated in terms of time-resolved dynamic light scattering (DLS) and rheological measurements during the cooling process. A drastic increase in the scattering intensity, ergodic-nonergodic transition, and a power-law behavior in the scattering intensity-time correlation function were observed at the gelation temperature T_gel. Thus obtained “microscopic” T_gel was confirmed to be in good agreement with a “macroscopic” T_gel obtained by rheological measurements irrespective of gelatin concentration C. The fractal exponent D_p evaluated by DLS was found to be q and C independent and was also in good agreement with that obtained by rheology (n), i.e., D_p≅n≅0.73, where q is the magnitude of the scattering vector.