Active Packaging of Immobilized Zinc Oxide Nanoparticles Controls Campylobacter jejuni in Raw Chicken Meat

Abstract

Zinc oxide nanoparticles (ZnO NPs) are regarded as a safe and stable antimicrobial that can inactivate bacteria by several potential working mecha-nisms. We aimed to incorporate ZnO NPs into packaging material to control Campylobacter in raw chicken meat. ZnO NPs were first incorporated into three-dimensional (3D) paper tubes to identify the lethal concentration against Campy-lobacter jejuni, which was selected as the working concentration to develop 2D functionalized absorbing pads by an ultrasound-assisted dipping technique. The functionalized pad was placed underneath raw chicken meat to inactivate C. je-juni and the predominant chicken microbiota at 4°C within 8 days of storage. Im-mobilized ZnO NPs at 0.856 mg/cm2 reduced C. jejuni from ~4 log CFU/25 g raw chicken meat to an undetectable level after 3 days of storage. Analysis by induc-tively coupled plasma-optical emission spectroscopy showed that the Zn level in-creased from 0.02 to 0.17 mg/cm2 in treated raw chicken meat. Scanning elec-tron microscopy validated the absence of nanoparticle migration onto raw chicken meat after treatment. Inactivation of C. jejuni was associated with the in-crease of lactic acid produced by Lactobacillus in raw chicken meat in a pH-dependent manner. Less than 5% of Zn2+ was released from ZnO NPs at neutral pH, while up to 88% was released when the pH was <3.5 within 2 days. Whole-transcriptome sequencing (RNA-Seq) analysis demonstrated a broad effect of ZnO NPs on genes involved in various cellular developmental processes as anno-tated by gene ontology. Taken together, the results indicate that functionalized absorbing pads inactivated C. jejuni in raw chicken meat by immobilized ZnO NPs along with the controllable released Zn2+. IMPORTANCE Prevalence of Campylobacter in raw poultry remains a major food microbiological safety challenge. Novel mitigation strategies are required to en-sure the safety and quality of poultry products. Active food packaging can con-trol pathogens without directly adding antimicrobials into the food matrix and extend the food's shelf life. The functionalized absorbing pad with ZnO NPs de-veloped in this study was able to inactivate C. jejuni in raw chicken meat and keep the meat free from C. jejuni contamination during shelf life without any ob-served migration of nanoparticles. The controllable conversion of immobilized ZnO NPs to free Zn2+ makes this approach safe and eco-friendly and paves the way for developing a novel intervention strategy for other high-risk foods. Our study applied nanotechnology to exploit an effective approach for Campylobac-ter control in raw chicken meat products.