There is currently a growing interest in developing antibacterial polymeric food packaging materials to prolong the shelf life of packaged food. The industry actively seeks environmentally friendly and straightforward techniques to create polymeric films with advanced functionality, ensuring no harm to consumers. In line with this, this study focuses on fabricating antibacterial PEG-like coatings enriched with nitrogen-containing groups. The goal is achieved through atmospheric pressure aerosol-assisted plasma polymerization using tri(ethylene glycol) divinyl ether as a monomer. Various nozzle geometries of the plasma head alter the deposition process and are used to control the monomer residence time, allowing direct incorporation of nitrogen-containing functional groups during PEG plasma polymerization. A comprehensive physicochemical characterization of the deposited coatings was conducted using various surface characterization tools. The antibacterial activity against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus was assessed. To ensure safe usage for food applications, the degradation products released from the coatings immersed in water and diverse food simulants, were identified by LC-MS. Subsequently, toxicity evaluation based on chemical structure was conducted. Optimizing monomer residence time enables the production of smooth, conformal coatings with high hydrophilicity, retained PEG functionality, and nitrogen-containing functional groups. These coatings exhibit remarkable antimicrobial activity against E. coli (4.8 log reduction) and S. aureus (2.1 log reduction), primarily due to the nitrogen functionalities. Regarding the degradation products, a total of 14 degradation products was found, with variations in the number of ethylene oxide groups, showcasing the efficiency of the plasma polymerization approach. The potential toxicity evaluation suggests that the released substances are non-toxic. In conclusion, these developed coatings are promising materials to be safely used as antibacterial food packaging.

Frank Devlieghere

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