Antibacterial and Freshness-Preserving Mechanisms of Chitosan-Nano-TiO₂-Nano-Ag Composite Materials

With chitosan, nano-TiO₂ and nano-Ag as raw materials, nano-TiO₂ and nano-TiO₂-Ag were modified by a surface modifier-sodium laurate. Chitosan (CTS), chitosan-nano-TiO₂ (CTS-TiO₂), and chitosan-nano-TiO₂-nano-Ag (CTS-TiO₂-Ag) composite materials and corresponding films were prepared by a solution co-blending method. Then, the antibacterial performances of the above three types of materials against Escherichia coli, Staphylococcus aureus, and Bacillus subtilis were compared. Moreover, potato and strawberry weight loss rates, peroxidase activity, and vitamin C contents after different film coating treatments were measured. Compared with CTS films, the CTS-TiO₂-Ag and CTS-TiO₂ composite films both showed better physical properties, and both demonstrated higher antibacterial effects, especially for E. coli. Measurement of physiological indices in fruits and vegetables showed that the freshness-preserving effect of CTS-TiO₂-Ag coating films was the most significant. In all, the CTS-TiO₂-Ag coating films can actively contribute to the storage of fruits and vegetables at room temperature, and better ensure product quality. Thus, such films are meaningful for research and development of new fruit freshness-keeping techniques and materials.