Preparation and characterization of antioxidant, antimicrobial and pH-sensitive films based on chitosan, silver nanoparticles and purple corn extract

In this study, silver nanoparticles (AgNPs) and anthocyanin-rich purple corn extract (PCE) were incorporated into chitosan to develop active and intelligent food packaging films. The structural, physical and functional properties of chitosan/AgNPs/PCE films were compared with those of chitosan, chitosan/AgNPs and chitosan/PCE films. Spectroscopic analysis showed seven kinds of anthocyanins were present in PCE. Some particles and spots appeared on the surfaces and cross-sections of composite films. Fourier transform infrared and X-ray diffraction analyses suggested the interactions between chitosan and AgNPs were based on coordination effect, whereas the interactions between chitosan and PCE were mainly established through hydrogen bonds. The incorporation of PCE and/or AgNPs remarkably promoted the light and water vapor barrier ability, mechanical strength, antioxidant and antimicrobial properties of chitosan film. Notably, chitosan/AgNPs/PCE film exhibited the highest barrier, mechanical, antioxidant and antimicrobial properties due to synergistic effect between PCE and AgNPs. Besides, chitosan/PCE and chitosan/AgNPs/PCE films could change their colors in different pH buffers because of abundant anthocyanins in PCE. Our results suggested chitosan/AgNPs/PCE film could be used as novel active and intelligent food packaging material in food industry.