Effects of Polyols and Sugars on the Sol-Gel Transition of Gelatin

The melting temperature of gelatin gel increased with increasing concentrations of polyols and sugars added at any gelatin concentation. The enthalpy of gel melting measured by Eldridge-Ferry plots and calorimetric measurements was decreased by addition of these polyhydric compounds, indicating that the gel stabilization by them is predominantly due to the large decrease in entropy of gel melting. Circular dichroism analysis showed that the helix formation of gelatin molecules was enhanced with increasing concentrations of these additives, but there was no positive correlation between their helix-forming ability and gel-stabilizing ability. The viscosity of gelatin solution was less in these mixed solvents than in water. Based on these results, a possible stabilization mechanism of gelatin gel by polyhydric compounds was discussed, in comparison with that of native collagen, in terms of the thermodynamics of protein-solvent interactions.