Effect of pine, eucalyptus, and corn straw nanofibers on the structural properties of rice flour-based biodegradable films

The objective of this study was to develop biodegradable films produced from broken grains of rice (agro-industrial byproducts), sorbitol, and pectin, and to evaluate the influence of pine (PN), eucalyptus (EN), and corn straw (CN) nanofibers on the opacity, solubility, water vapor permeability, mechanical properties, and morphology of the films. Two simplex-centroid designs were used for the variables. Sorbitol and pectin interacted satisfactorily with rice starch, making the film more flexible and transparent. The cellulose nanofibers (50% PN, 50% EN, and 50% CN) increased the film opacity (2.8–3.35% μm⁻¹) and decreased the water vapor permeability (0.035–0.037 g day⁻¹ m⁻²) and water solubility (0.96–5.59%) of the rice flour-based films (10 g of rice flour, 1.5 g of pectin, and 19.5 mL of sorbitol solution at 70 g·mL⁻¹). The PN, EN, and CN nanofibers improved the mechanical properties of the films: CN increased the elongation at break (6.32%) and hydrophobicity (72.12%); PN and EN increased the elasticity (20.50–25.31 MPa). The addition of combined nanofibers (PN+CN, EN +CN, and PN+EN) into the rice flour-based film (33:33:33) allows the film to be used as a coating and in food packaging.