Preparation and characterization of chitosan films with three kinds of molecular weight for food packaging.

Recently, chitosan film has been widely used to extend the shelf life of food. In this study, high, medium and low molecular weight of chitosan were used as raw materials to prepare a series of films (C1-C27) by controlling the content of chitosan and glycerol, and their mechanical properties, water vapor permeability (WVP), oxygen transmittance (OP), morphology and antibacterial properties were characterized as well. The results indicated that all films had film-forming properties. Among them, the film C16 with high molecular weight, high chitosan content and 50% glycerol/chitosan (w/w) exhibited the excellent transparency (91.2%), elongation at break (28.948%), tensile strength (77.963 MPa), WVP (1.46 × 10-12gcm/cm2·sPa), smooth morphology, denser structure and antibacterial property (Staphylococcus aureus and Escherichia coli). Meanwhile, the preservation properties of chitosan films were evaluated by strawberry preservation. Almost all the studied films had better preservation effect than the commercially available PE films, especially of which the film C16 was the best compared with others. It maintained the physical and chemical parameters (weight loss ratio, total soluble solids, titratable acidity, total ascorbic acid and color change) of strawberry most obviously. Hence, chitosan films had great potential for the industrial application of fruit preservation.