Relationship between triple-helix content and mechanical properties of gelatin films.

This paper reports a study on the influence of the renaturation level of gelatin on the mechanical and swelling properties of gelatin films. Films at different renaturation level were obtained from gelatin samples with different Bloom index. It was verified that the triple-helix content, calculated from the values of the enthalpy of denaturation associated to the endothermal transition at about 41 degrees C of gelatin, increases with the Bloom index. The d.s.c. data are further supported by the results of the X-ray diffraction investigation carried out on the same samples. The increase of triple-helix content provokes a significant reduction in the degree of swelling, and a remarkable improvement of the mechanical properties of the films. The elastic Young's modulus, E, increases linearly with the renaturation level, from 3.6 to 12.0 MPa. Crosslinking with GTA 1% remarkably reduces the degree of swelling of all the samples, and induces a further increase of the Young's modulus, which reaches values up to 27 MPa.