Effect of Chitosan Crosslinked with Citric Acid Coating on Kraft Paper for Food Packaging Applications

Abstract

Chitosan (CS) films were prepared by crosslinking them with citric acid (CA) at various concentrations (0, 0.1, 0.2, 0.3, 0.4, and 0.5 wt %, calculated based on the dry weight of CS). These films were prepared using the solution blending-casting method and then dried at 50°C for 15 h. The thickness, water activity (a_w), and water vapor permeability (WVP) of these films were investigated. The thickness of the films ranged from 0.30 to 0.60 mm, while the a_w of the films ranged from 0.48 to 0.55. Importantly, the properties of the films showed changes that correlated with the varying CA content, and Fourier transform infrared (FTIR) confirmed the crosslinking between CS and CA. Subsequently, kraft paper was coated with CS solution at different CA concentrations. Basis weight, water adsorption, oil resistance, puncture strength, and tear strength were measured. The results indicated that the properties of the CS films crosslinked with CA showed improvement when compared to the uncross-linked films. However, excessive CA addition in the films had negative effects due to the solidifying crystals of CA on the film surface. After 3 months, the degradation of the paper coating films reached 26.98%. The findings suggested that the kraft paper-coated chitosan crosslinked with 0.3 wt % CA exhibited the best overall properties. This study has the potential for application as a paper-coating film in the food industry.