THERMODYNAMIC PARAMETERS OF THE JUNCTION ZONES IN THERMOREVERSIBLE MALTODEXTRIN GELS

The standard breakdown entropy ΔS0 and Gibbs free energy ΔG0 of the junction zones in thermally reversible maltodextrin gels are calculated from thermal data as a function of the alignment coefficient P. Based on a value for P {reversed tilde equals} 170, ΔS0 and ΔG0 are 24 J mol-1 K and 18 kJ mol-1 respectively. The definition range of the equation for calculating ΔS0 and ΔG0 ends at P {reversed tilde equals} 210. This comes quite near the value P {reversed tilde equals} 170 for the magnitude of the coherent scattering units in maltodextrin gels as estimated by wide angle X-ray scattering. Maltodextrin gelation is a weakly cooperative process. Because of the low entropic effect, small changes in enthalpy result in the formation of thermodynamically stable gel structures. © 1990.