Kinetics of gelatin transitions with phase separation:: T-jump and step-wise DSC study

The isothermal gelation (or melting) of gelatin after fast cooling (or heating) steps: is studied by using high sensitivity differential scanning micro-calorimetry, in order to determine the dependence of the kinetic and thermodynamic parameters upon changes in composition and in temperature. The calorimetric heat flow curves, obtained according to defined temperature profiles, have been fitted with exponential functions (simple exponentials or stretched exponentials for the step-wise and for T-jump experiments, respectively). The gelation process of gelatin alone for t < 300 min shows that the characteristic time t and the fractional exponent are <beta> very sensitive to the concentration of gelatin chains and to the microscopic phase segregation due to the presence of another polymeric component. (C) 2001 Published by Elsevier Science B.V. All rights reserved.