Arrowroot Starch Films Cross-Linked with Citric Acid: Susceptibility to Water, Biodegradation, and Tensile Properties

In this study, thermoplastic arrowroot starch (TPA) films cross-linked with citric acid (CA) were prepared using solvent casting method. Different glycerol (25%, 30%, and 35%) and CA (5%, 9%, and 12%) contents were evaluated. The films were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD), as well as by their transparency, thickness, mechanical properties, swelling, moisture content, solubility, water vapor permeability, and soil degradation. FTIR results showed the formation of ester linkages, confirming the cross-linking of arrowroot starch with CA. XRD revealed broad peaks at approximately 20° for all films, characteristic of the amorphous phase of starch. The SEM micrographs revealed more homogeneous and continuous surfaces in the cross-linked films. For films with 30% glycerol, cross-linking increased the tensile strength from 1.74 MPa for the glycerol-free film (TPA-30/CA-0) to 6.60 MPa for the film with 9% CA (TPA-30/CA-9). Additionally, the CA-cross-linked TPA films exhibited less swelling in water for all the evaluated periods. In the soil degradation test, TPA films with CA exhibited slower degradation, with total degradation observed after 18 days. Bread stored with TPA-30/CA-9 and TPA-25/CA-12, exhibited a delay in fungal growth. Thus, based on our results, the TPA-30/CA-9 film presents a suitable potential for use in the food packaging sector.