Investigation of Physical, Mechanical and Morphological Properties of Chitosan Film Prepared with Different Levels, Molecular Weights and Solvents

Using of chitosan biopolymer has been developed in the form of edible film and coating as a packaging material for food products. The physical and mechanical properties of chitosan film are influenced by various factors. To investigate the impact of effective factors on the film-forming solution, the present experiment in a completely randomized design using the 23 factorial method, a total of 8 treatments including the level (2 and 4%), molecular weight (high and low) of chitosan and solvent type (acetic acid and citric acid) used in film preparation was carried out. The physical and mechanical parameters of the films were measured. Also, the microstructure of the films was investigated using scanning electron microscope (SEM) images and infrared spectroscopy (FTIR) spectra. The results showed that 4% high and low molecular weights chitosan films which were dissolved in the acetic acid had the highest tensile strength (0.16 ± 0.01 MPa), Young's modulus (2.45 ± 0.55 MPa) and impermeability (2.17 ± 0.09 ± 0.09 g/msPa), and the highest elongation at break (54.33% ± 0.95%) was observed in 4% high molecular weight chitosan film with citric acid solvent (p<0.05). In addition, high molecular weight chitosan film dissolved in acetic acid was more transparent compared to citric acid (p<0.05). SEM images and IR spectra analysis confirmed the obtained results. Therefore, the physical and mechanical performance of the chitosan film was affected by the level and molecular weight of chitosan, and especially the type of acidic solvent, as well as the interaction effects of these factors. In general, the use of a higher level and molecular weight of chitosan leads to the production of a better film, and acetic acid is a more suitable solvent than citric acid.