**5.1 Mechanical property**

The edible bio-based film can resist normal external force created during handling and must have the proper mechanical property [155]. Mechanical property means film should be most effective in case of tearing resistance, stiffness, tensile strength, puncture resistance, bursting strength, etc. [61, 87]. Adequate mechanical strength ensures the integrity of a film and its freedom from minor defects, such as a pin hole, which ruin the barrier property. Coatings can also lessen damages to foods during handling and transportation. Sometimes, edible coatings and films may be used to change handling properties of materials. For example, edible films can encapsulate liquids or powders to improve handling. Simple protein films are stronger and more stretchable than composite films containing lipids. Lipid content was linearly associated to strength reduction. A WPC protein emulsion film with lipid of higher melting point exhibited better mechanical strength than that with lipid of a lower melting point [165]. Polysaccharide has lesser mechanical property than protein-based film. In the mechanical properties of the edible film, essential oil plays a vital role. Plasticiser helps to decrease tensile strength and increase the elongation property of edible film [112].
