Abstract:To develop food preservation materials with better performance and biodegradability, edible composite membranes were prepared using chitosan and gellan gum as raw materials. In the present work, chitosan was modified via carboxymethylation and cholic acid, which conferred amphiphilic properties and allowed ready dissolution of the modified chitosan in water. Gellan gum was modified via carboxymethylation to prevent gel formation and make it uniformly water-soluble at room temperature. The structures of the modified materials were characterized using Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. The modified chitosan was used as the main film-forming material, gellan gum as the reinforcing phase, and glycerol as the plasticizer in the preparation of amphiphilic chitosan/modified gellan gum composite membranes. Subsequently, the mechanical, thermal, and optical properties of the composite membranes were investigated. Results indicated that, under conditions of drying at 55 ℃ for 24 h wherein the mass ratio of amphiphilic chitosan to modified gellan gum was 5:2 and the content of added glycerol was 2%, the temperature at which the thermal degradation rate of the composite membrane reached a maximum was increased to approximately 260 ℃. Moreover, a membrane transparency of 84% was achieved. Tensile strength reached a maximum of 3.35 MPa, and the elongation at break was increased to 111.00%. Under these conditions, the composite membrane achieved optimum thermal stability and mechanical properties, high transparency, and good sensory evaluation results. Therefore, the addition of gellan gum improved the thermal stability and mechanical properties of chitosan.
