Antimicrobial properties of poly (vinyl alcohol) films with zeolitic imidazolate framework (ZIF-8) nanoparticles for food packaging.

Abstract

Antimicrobial packaging films are of interest to the fresh produce industry due to the high number of foodborne illness outbreaks associated with these products. This study evaluated the antimicrobial effectiveness of poly (vinyl alcohol) (PVA) films with embedded zeolitic imidazolate framework (ZIF-8) nanoparticles carrying trans-cinnamaldehyde (TC) against Escherichia coli MG1655 in spinach leaves. PVA films were synthesized using distilled water and mixed at 90°C for 1h. The synthesized nanoparticles were introduced at various mass ratio concentrations (0%-5% weight of ZIF-8@TC nanoparticles to PVA), namely PVA-Z8-0 (control) through PVA-Z8-5. The PVA and ZIF-8@TC solution was mixed for 24h until it seemed homogenous, cast, and dried in a ventilated oven at 35°C for 24h. The release rate of TC from the PVA/ZIF-8@TC into both ethanol and methanol was characterized using HPLC methods. Disk diffusion and growth studies were performed to quantify the films antimicrobial effectiveness. Disk diffusion test showed that antimicrobial activity against E. coli MG1655 increased (p <0.05) with increased nanoparticles concentration. Growth characteristics were described by the Baranyi model with some variations. About 0.26, 0.73, and 1.65 log reductions were achieved with the PVA-Z8-1 to PVA-Z8-3 films, respectively, while total inactivation was achieved with both the PVA-Z8-4 and PVA-Z8-5 films (p <0.05). Similarly, the Baranyi model described the inhibitory profiles of the different films. This study contributes to the overall food safety body of knowledge regarding fresh produce and other packaged foods through the development of biopolymeric films with embedded nanoparticles to entrap natural antimicrobials. PRACTICAL APPLICATION: This study paves the way for further research on the development of active polymeric films for food packaging applications.