Preparation and characterization of thymol-loaded ZIF-8/κ-carrangeenan/Zein composite film as active food packaging with enhanced functional properties for blueberry preservation

Abstract

Polysaccharide-protein-based composite films are promising for food packaging, but interfacial incompatibility between hydrophilic biopolymers and hydrophobic proteins limits their use. In this study, a new thymol-loaded zeolitic imidazolate framework-8/κ-carrageenan/Zein composite film was developed for blueberry preservation. The film exhibited excellent physical properties with a thickness of 0.052 ± 0.0001 mm, a high tensile strength of 40.631 ± 1.527 MPa, an elongation at break of 21.223 ± 1.018 %, and a reduced water vapor permeability of (0.764 ± 0.166) × 10^-8 kg·m·m^-2·s^-1·Pa^-1. The incorporation of thymol and ZIF-8 improved the film's microstructure and interfacial compatibility between κ-carrageenan and Zein. Thymol release was pH-dependent and sustained with a cumulative release of 91.959 ± 0.454 % over 36 h at pH 4.5. Biological testing revealed significant antibacterial properties with survival rates of 0.002 ± 0.002 % against Staphylococcus aureus and 5.973 ± 0.307 % against Escherichia coli, and antioxidant capacity with DPPH and ABTS radical scavenging rates of 75.60 ± 0.53 % and 61.49 ± 1.19 %, respectively. The film showed good biodegradability and extended blueberry shelf life by 9 days. This composite film offers enhanced mechanical properties, controlled release, and bioactivity, showing great potential as active food packaging for fruit preservation.

Keywords: Antibacterial activity; Fruit preservation; Nanoparticles; ZIF-8; Zein; κ-Carrangeenan.