Effect of molecular structure on the thermal properties and water sorption of thin gelatin films

The thin gelatin films, prepared by casting of gelatin solutions at different drying temperatures, had different molecular morphologies as monitored, using wide angle X-ray diffraction and differential scanning calorimetry techniques. It was revealed that gelatin films dried at lower temperatures showed markedly higher crystalline or helical structure with slightly higher Tg and lower ΔCp than those for the hot dried film with more coiled structure. These films exhibited different interactions with water, which were assessed, using dynamic vapour sorption experiments. The sorption capacity of these films increased with increasing the degree of molecular order. There was no difference between the diffusion coefficients obtained upon sorption and desorption steps for each gelatin samples. The diffusion coefficient did not show any significant dependence on water content