Gelation of aqueous gelatin solutions. I. Structural investigation

We have investigated the structural modifications of aqueous gelatin solutions for various thermal treatments and different concentrations. The structure is explored at different microscopic levels, putting into evidence the conformational coil ~ helix transition of the proteic chains (by optical rotation), the supramolecular structure of the network (by electron microscopy) and the role of solvent (by proton nuclear magnetic resonance). The non-equilibrium nature of the gel phase is demonstrated as well as its disordered character. A phenomenological analysis of the kinetics of helix formation is proposed, followed by an attempt for a microscopic modelling of the mechanisms, based on the data presently known.