Physicochemical and antimicrobial properties of chitosan composite films incorporated with glycerol monolaurate and nano-TiO2

Antimicrobial composite films for active food packaging were developed based on chitosan, glycerol monolaurate (GML), and nano-TiO2. The rheological, morphological, physical, and antimicrobial properties of chitosan-based composite films doped with GML and nano-TiO2 were investigated. All film-forming solutions showed typical pseudoplastic properties, and the viscosity of film-forming solutions increased after the addition of GML. The chitosan films incorporated with GML were transparent, and the transparency of films decreased after adding nano-TiO2. The chitosan-TiO2 composite film containing 1.5% GML exhibited the highest UV–vis barrier properties. Scanning electron microscopy images showed that the surface of films containing GML presented a rough structure, and the changes in the microstructure of films were also confirmed by the results obtained using atomic force microscopy. The addition of GML and nano-TiO2 improved the water-resistance and the barrier properties of the chitosan film. Increasing the GML content resulted in increased water contact angle and decreased the permeability of water vapor, oxygen, and carbon dioxide of composite films. Moreover, the incorporation of GML reduced the tensile strength of composite films. Fourier transform infrared spectroscopy and X-ray diffraction indicated that the interaction among chitosan, GML, and nano-TiO2 could be established through non-covalent bonds. Notably, chitosan-based composite films doped with GML and nano-TiO2 exhibited strong antimicrobial activity, and the film containing 1.5% GML was the most effective. The structure of bacterial cells was injured by the composite films. Overall, the developed composite films exhibited excellent functional properties and could be potential targets for bioactive packaging.