Effects of citric acid on properties of chitosan/chitin nanofiber composite films

Biocomposite films have gained increasing interest in the development of packaging
materials to preserve the quality of food. In particular, chitosan has been widely used as a biopolymer
for active food packaging due to its biodegradability and antimicrobial activities. However, neat
chitosan films have limitations including poor mechanical strength, weak barrier properties, and high
water absorption. To overcome these problems, chitin nanofibers and citric acid were added into
chitosan films as a reinforcing and a crosslinking agent, respectively. Thus, the aim of this study was
to prepare chitosan/chitin nanofiber composite films with various concentrations of citric acid via a
solvent casting method, and the effects of citric acid concentrations (0-20 wt %) on the properties of
the composite films were investigated. Fourier transform infrared (FT-IR) spectra confirmed that
citric acid was successfully crosslinked with chitosan and chitin nanofibers. The results revealed that
the incorporation of 10 wt % citric acid was the optimal condition to enhance the mechanical and
water resistance properties of the composite films in comparison with those of the un-crosslinked
films. Hence, cross-linked chitosan/chitin nanofiber composite films have potential for the food
packaging application.