The force (N) and deformation (mm) were determined by
performing puncture tests using a texture analyzer (TA, TX2i stable
micro system, England). Samples of 40 mm diameter each
were fixed using a tape on the plate of the equipment with a
hole of 20 mm diameter. A cylindrical probe of 5 mm diameter
was moved perpendicular to the film surface at a constant
speed of 1 mm s−1 until the probe passed through the film. The
force–deformation curves were plotted and at rupture point force
and deformation were recorded by analyzing ten samples for each
test.