Chitosan/kudzu-based packaging films synergistically reinforced by paeonol@ZIF-8 and Ag2CO3/Ag2O nano-heterojunctions for raspberry preservation

Abstract

Chitosan film is frequently used to preserve food. However, the stability of chitosan film is poor, so it is crucial to strengthen the stability, anti-ultraviolet, antibacterial activity, anti-oxidation and continuous fresh-keeping activity of chitosan film. In this work, paeonol@ZIF-8 and Ag₂CO₃/Ag₂O nano-heterojunctions were dispersed into chitosan/kudzu-based solution by matrix mixing and solution casting method, which successfully prepared a biodegradable nanocomposite film and used it for preservation of raspberry. Moreover, ZIF-8 provided a large number of active sites to PAE. The loading rate of PAE@ZIF-8 was 36.33 ± 0.82 % by a simple one-pot process. The paeonol@ZIF-8 had the effect of slow release in different food environments and intelligent response to pH. The Ag₂CO₃/Ag₂O nano-heterojunctions also cooperated to inhibit bacteria by releasing silver ions. Meanwhile, the physical and chemical properties of chitosan film were improved, which could make it more suitable for food packaging. The improved film could block 90.32 % of UV–visible light. Moreover, its antioxidant and antibacterial properties were increased by 1.24 times and 4 times, respectively. It could extend the shelf life of raspberries to 5 days as the hydrophobic film. The nanocomposite film also effectively maintained cucumber slice quality. It also found that the migrating silver ion content of raspberry and cucumber slice complied with EU food safety law regulations. Importantly, the nanocomposite film was degradable and did not affect the germination and growth of the seed. Our work provides a sustainable multifunctional food packaging material that can be used to preserve perishable foods.