Development of polylactic acid based antimicrobial food packaging films with N-halamine modified microcrystalline cellulose

Bio-based "green" films with superior antimicrobial activity were developed from polylactic acid (PLA) and cyclic N-halamine 1-chloro-2,2,5,5-tetramethyl-4-imidazolidinone (MC) grafted microcrystalline cellulose (MCC) fibers (herein referred to as g-MCC). The structure of g-MCC was characterized by Fourier Transform Infrared (FT-IR) and Nuclear Magnetic Resonance (NMR) spectroscopy. Results indicated N-halamine MC was successfully grafted onto MCC fibers, with a grafting percentage of 10.24 %. The grafting improved compatibility between g-MCC and PLA, leading to an excellent dispersion of g-MCC in the film matrix, and a superior transparency of the g-MCC/PLA compared to that of the MCC/PLA films. Additionally, the enhanced compatibility the g-MCC/PLA films produced better mechanical properties including mechanical strength, elongation at break and initial modulus than those of both MCC/PLA and MC/PLA composites. With N-halamine, g-MCC/PLA completely inactivated all the inoculated Escherichia coli and Staphylococcus aureus within 5 and 30 min of contact, respectively. More importantly, the migration test showed that the oxidative chlorine of g-MCC/PLA was highly stable than that of MC/PLA films, providing a long-term antimicrobial activity. Finally, preservation test con-ducted on fresh bread slices further demonstrated its promising applications in the food industry.