Abstract: Multifunctional food packaging films were prepared using polyvinyl alcohol (PVA) and chitosan (CS) as film-forming substrates, montmorillonite (MMT)-supported tea polyphenol (TP) as a bacteriostatic agent, and bromocresol purple (BCP), methyl red (MR) or their combinations as an indicator. The effects of BCP, MR and their combination as well as MMT-supported TP on the physical and functional properties of the films were studied, and they were applied to monitor the freshness of chilled pork. The results showed good compatibility between these components. The addition of the indicator enhanced the crystallinity of the blend film and improved its physical and optical properties. The indicator film could respond to ammonia gas, and the highest sensitivity was obtained with a 1.5:1 (m/m) combination of BCP and MR. The addition of bacteriostatic agent significantly improved the water resistance, water vapor barrier performance, antioxidant performance and bacteriostatic performance of the film. When applying the most sensitive antibacterial indicator film to monitor the freshness of chilled pork, a significantly positive correlation was found between the color changes of the film and the freshness of chilled pork, and compared to the control group, the shelf life of chilled pork in the experimental group was extended by 1 to 2 days, indicating that the antibacterial indicator films can real time monitor the freshness and effectively extend the shelf life of chilled pork.

Key words: multifunctional food packaging film; polyvinyl alcohol; chitosan; tea polyphenols; bromocresol purple; freshness; preservation