Preparation and characterization of sodium alginate films with propolis extract and nano-SiO2

The objective of this work was to evaluate the effect of green propolis extract (PE) and silica nanoparticles (SiO2) on the structure of sodium alginate-based films (SA), as well as their physical and antioxidant properties. Control samples (only SA), films with SA and PE (SA/PE3%), as well as films simultaneously containing SA, PE and SiO2 (SA/PE3%/SiO25% and SA/PE3%/SiO210%) were systematically evaluated. Scanning electron microscopy revealed homogenous distribution of PE and SiO2 within the film matrix. The addition of both compounds increased tensile strength from 12.9 ± 1.2 (control) to 19.6 ± 1.4 MPa (SA/PE3%/SiO210%), without noting any extreme changes in elongation at break or modulus of elasticity. Additionally, the incorporation of PE provided an outstanding UV light blocking effect, and strong DPPH radical-scavenging activity for all samples, therefore, suggesting their potential for future application in active food packaging.