Aloe vera-capped ZnO nanoparticles loaded in polyvinyl alcohol/chitosan as biodegradable, UV-blocking, and antibacterial film for fruit packaging

Abstract

The fabrication of active food packaging materials from biodegradable polymers combined with metal and metal oxide nanoparticles has received significant research attention. Among them, ZnO nanoparticles have been widely used in food and pharmaceutical fields due to their low cost and broad-spectrum antibacterial efficacy. Herein, uniform ZnO nanoparticles (~ 53 nm in diameter) with single-phase crystallinity were green synthesized at moderate temperature (80 ℃) by using Aloe vera extract as capping agents and sodium hydroxide for pH adjustment. These Aloe vera-capped ZnO nanoparticles were incorporated into polyvinyl alcohol/chitosan (PVA/CS) films at varying contents for fruit packaging. The effects of the amounts of ZnO nanoparticles (0, 1, 3, 5, 10%) and glycerol (0, 5, 10, 20, 30%) relative to the weight of PVA on the film’s properties were investigated. The results show that the film containing 3% ZnO and 10% glycerol exhibits significant improvements in mechanical properties, water resistance, contact angle, water vapor transmission rate, thermal stability, and antibacterial efficiency compared to pristine PVA/CS films. Additionally, the loading amount of glycerol plays critical role in modulating the film’s mechanical properties. Furthermore, the antibacterial activities of the ZnO-loaded PVA/CS films against E. coli increase with the ZnO content, achieving bacterial growth reduction from 4 to 10 Log cfu/mL as the loaded amount of ZnO nanoparticles increases from 3% to 10%. The ZnO-loaded PVA/CS films also offer an excellent UV-blocking effect, effectively protecting green apples from UV radiation. Remarkably, green cherry tomatoes packed by these composite films retain freshness after 15 days of storage. These results highlight the great potential of the ZnO-loaded PVA/CS film as multifunctional active food packaging materials.

Graphical abstract