Incorporating curcumin grafted cellulose nanofiber into chitosan films with strong and high UV barrier properties

Chitosan has attracted much attention for antimicrobial food packaging because of its unique antibacterial property and excellent film forming ability, however their poor barrier and mechanical properties limit the application.
Thus, in this study, curcumin grafted cellulose nanofiber was applied to improve the mechanical and UV shielding properties. Modified cellulose nanofiber was obtained via grafting curcumin to TEMPO-oxidation cellulose, then bio-nanocomposite films composed of chitosan (100-67 wt%) and modified cellulose (0-33 wt%) were prepared by casting method. Infrared spectroscopy and X-ray photoelectron spectroscopy results indicated that cellulose was successfully modified. Scanning electron microscopy images and X-ray diffraction analysis showed that the addition of modified cellulose noticeably affected the morphology and crystal structure of the composite films. Moreover, the appropriate proportion of modified cellulose improved the oxidation resistance, tensile strength and UV barrier properties compared to pure chitosan films. It is also worth mentioning that the composite films maintained equivalent antibacterial activities incorporating with modified nanocellulose, although the ratio of chitosan was decreased. Furthermore, the water solubility of films decreased with the addition of modified cellulose nanofiber. It is concluded that curcumin grafted cellulose nanofiber significantly improved the mechanical and UV barrier properties of chitosan films. The findings in this work would provide useful information for application of chitosan in food packaging.