By adding gelatin tensile strength is increased significantly.
The strength at break can increase with the addition of dry matter, in our case gelatin, providing an increase in the number of superficial protein chains that are responsible for the enhance in the intermolecular interactions.
The thickness is another factor that may have contributed to increase the tensile strength. Park and Chinnan (1995) observed that the stress and fracture strain increased with the thickness of films of hydroxypropyl cellulose.