Preparation, properties, and characterization of modified sesbania gum composite film

Natural biodegradable packaging materials have become the focus of current research due to increased environmental consciousness and emphasis on food safety. In this paper, H2O2 was utilized to modify sesbania gum (SG), a natural polymer material, to prepare oxidized Sesbania gum (OSG), which was employed as the substrate for film formation. We created an antibacterial food packaging material by blending OSG with sodium carboxymethyl cellulose (CMC), glycerin, and nano-zinc oxide (Nano-ZnO), which acted as reinforcement agent, plasticizer, and bacteriostatic agent respectively. Fourier-transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were used to characterize the composite films, and the effects of Nano-ZnO additions on the mechanical properties and barrier properties of the composite films were investigated. The results showed that oxidation modification of sesbania gum increased film-forming properties, hydrophobicity and thermal stability, while also mitigating its distinct, undesirable odor. The tensile strength (TS) of the composite film firstly increased and then decreased, and the elongation at break (EAB) gradually decreased as the addition of Nano-ZnO increased from 0.1 mg/mL to 0.5 mg/mL. When the Nano-ZnO content is 0.3 mg/mL, the TS of the composite film reaches its maximum value of 19.25 MPa and the EAB is 30.04%. However, when further increasing the Nano-ZnO content, there was a slight decrease in TS and a significant decrease in EAB. Simultaneously, with the increase in the Nano-ZnO addition, the barrier property and thermal stability of the modified composite film were improved, and the light transmittance decreased from 78.94% to 30.39%. XRD proved that the four materials had good miscibility. SEM showed that Nano-ZnO was agglomerated, and the surface of the film became rough when the Nano-ZnO amount was more than 0.3 mg/mL. SG-modified composite film can be used as a new food packaging material, providing a new idea for the preparation of food packaging materials and expanding the application of SG.