Modified chitosan: A step toward improving the properties of antibacterial food packages

• A new antibacterial polymer is obtained by grafting polyethylene glycol chains onto chitosan.
• The chitosan–polyethylene glycol conjugate displays improves compatibility with polyethylene.
• The antibacterial properties are not hampered by the modification of chitosan.

Current needs for minimally processed food products are spurring the development of antibacterial packages and necessitate new antibacterial additives capable of merging with plastic bulk material. We present a new approach that can potentially improve the physical properties of antibacterial packaging by enhancing the compatibility between the main polymeric ingredient of the package and an antibacterial additive. Enhance compatibility of chitosan, a polysaccharide with known antibacterial properties, was obtained by conjugating polyethylene glycol (PEG) onto chitosan to create PEGylated chitosan. We show that the PEG conjugation does not hamper the antibacterial properties of the chitosan. Moreover, the PEGylated chitosan film exhibited antibacterial activity which was absent in the native chitosan film. Improved compatibility with polyethylene films, leading to better transparency compared to films compounded with native chitosan, is demonstrated. The thermal behavior of the film is governed by the bulk polyethylene due to the small concentration of the PEGylated chitosan, yet the footprint of the additive is detectable. The addition of PEGylated chitosan decreases the Young modulus, which was assumed to be responsible for the compatibilizing effect of the grafted PEG side chains.