Physicochemical and mechanical properties of cellulose nanofiber-shellac composite edible films

This study examined the physicochemical and mechanical properties of edible composite films made of cellulose nanofiber (CNF) and shellac (Sh). All films were conditioned at 25°C and 53% relative humidity (RH) for at least 48 h before analyses. Increasing the Sh ratio from 0% to 100% resulted in an increase in film thickness from 57.8 μm to 71.1 μm, while opacity decreased significantly from 22.3 mm−1 to 3.7 mm−1. With the increase in the Sh ratio, the moisture content, water solubility, and swelling of the film increased from 9.7% to 35.1%, 4.9% to 100%, and 3.0% to 10.5%, respectively. The CNF film (0% Sh) exhibited a lower water contact angle than the films with 80% and 100% Sh, but it was more water-resistant. As the Sh ratio increased, the tensile strength, yield stress, Young’s modulus, and work of break of the films decreased significantly from 17.9 MPa to 0.3 MPa, 1.00 MPa to 0.38 MPa, 220.7 MPa to 0.9 MPa, and 0.67 MJ/m3 to 0.13 MJ/m3, respectively. Conversely, the elongation at break increased dramatically from 10% to 253%. This study demonstrated that the thickness, opacity, moisture-related properties, and mechanical properties of CNF-Sh composite films could be tailored by varying the biopolymer ratio.