Improvement of mechanical and heat-sealing properties of edible chitosan films via addition of gelatin and CO treatment of film-forming solutions.

Glycerol, gelatin and CO were used to prepare chitosan-based packaging films with improved mechanical properties and seal strength. Nuclear magnetic resonance spectroscopy, X-ray diffraction analysis, Fourier transform infrared spectroscopy and dynamic mechanical analysis were conducted; the results were used to explain the mechanical and sealing properties data. Film color was also measured. Combined addition of glycerol and use of CO to treat the film-forming solution led to decreased film crystallinity and glass transition temperature, resulting in improved film mechanical properties. Addition of glycerol and gelatin resulted in enhanced molecular interactions between chitosan-gelatin and improved sealability of the films. Films with the best mechanical and sealing properties were obtained from a solution with 25% (w/w) glycerol and treated with CO and from that with 25% (w/w) glycerol and 10% (w/v) gelatin, respectively. Films with addition of both glycerol and gelatin exhibited lower lightness, but higher yellowness than the commercial stretch film.