Physicochemical aspects of the higher order structure of gelatin in dilute aqueous solution

The conversion of collagen to gelatin results in a heterogeneous product with a broad molecular weight profile (MWP). Addition of a non-solvent, such as ethanol, to gelatin solutions gradually causes the Florey-Huggins solvent-protein interaction parameter to exceed the critical value for the different molecular weight fractions, causing desolvation of the polymer. When sufficient solvent molecules are removed, the gelatin molecules begin to aggregate, resulting in phase separation, and forming a coacervate. Modification of the net charge of the protein, by adjusting the solution pH to values ranging about the iso-electric point (IEP), influences the degree of interaction between the different molecular weight fractions, and hence the response of the protein to non-solvent. 1