Thermodynamic Analysis of Sol-Gel Transition of Gelatin in Terms of Water Activity in Various Solutions

Sol-gel transition of gelatin was analyzed as a multisite stoichiometric reaction of a gelatin molecule with water and solute molecules. The equilibrium sol-gel transition temperature, T-p, was estimated from the average of gelation and melting temperature measured by differential scanning calorimetry. From T-t and the melting enthalpy, Delta H-sob, the equilibrium sol-to-gel ratio was estimated by the van't Hoff equation. The reciprocal form of the Wyman-Tanford equation, which describes the sol-to-gel ratio as a function of water activity, was successfully applied to obtain a good linear relationship. From this analysis, the role of water activity on the sol-gel transition of gelatin was clearly explained and the contributions of hydration and solute binding to gelatin molecules were separately discussed in sol-gel transition. The general solution for the free energy for gel-stabilization in various solutions was obtained as a simple function of solute concentration. (C) 2015 Wiley Periodicals, Inc.