High UV-shielding polyvinyl alcohol/chitosan-based transparent bioplastic film for food preservation

Abstract

The bioplastic film polyvinyl alcohol (PVA) /chitosan (CS), i.e., PC, formed by blending PVA with CS, exhibits excellent antioxidant properties and biodegradability. However, it lacks ultraviolet (UV) blocking ability, limiting its capacity to protect adipose-rich foods from photo-oxidation. Lignin possesses remarkable UV shielding ability that inhibits food photo-oxidation and extends shelf-life. However, the dark brown color of lignin negatively impacts the film color and transparency. To address these restrictions, this study incorporated acetylated lignin (ALG) loaded with halloysite nanotubes (HNTs) into conventional PC films (PC-HALG), resulting in a significant reduction in the color intensity of the film by almost 255.3 %, i.e., almost being colorless. The UV-A and UV-B shielding capacities of the PC films were increased by 1347 % and 617 %, respectively. Thus, ALG provided the PC films with excellent UV shielding capacity while reducing their color intensity and maintaining high transparency. Additionally, the loading of HNTS reduced lignin agglomeration, contributing to the improvement in transparency and enhancement of UV shielding effects in PC films. Furthermore, the PC-HALG film retained and even enhanced the biodegradability of the PC film, which exhibited degradability within one week. Freshness preservation experiments confirmed that the oxidation of pecan oil covered with the PC-HALG film under UV irradiation was reduced by 81.3 %–92.2 %. These findings suggest that this bioplastic film can be used in visually displaying food products while preventing their photo-oxidation. Mechanical properties, thermal stability, barrier properties, and antioxidant properties of the developed PC-HALG film were also characterized.