Advanced biopolymer films for sustainable applications: Integrating Fe₃O₄ and ZnO nanoparticles into pea protein isolate-alginate matrices.

This study aimed to develop an innovative approach for electrically and magnetically responsive smart films based on pea protein isolate (PPI) and alginate. The effects of varying concentrations of Fe₃O₄ (5 % and 10 %) and ZnO (3 % and 6 %) nanoparticles on the physical, mechanical, structural, barrier, thermal, chemical, antimicrobial, and electrical properties of the films were evaluated. Results revealed that increasing the nanoparticle concentration enhanced the thickness and mechanical strength of the films by 29.2 % and 13.8 %, respectively. Interactions between nanoparticles and the biopolymer structure were confirmed through FTIR analysis, which also demonstrated improved thermal stability and uniform structure. The addition of nanoparticles induced significant changes in the surface morphology, forming a relatively compact and homogeneous matrix. These modifications reduced water vapor and oxygen permeability by 41.8 % and 39.9 %, respectively. Furthermore, increased nanoparticle concentrations elevated the opacity and darkness of the composite films while decreasing their whiteness index. Elemental analysis using energy-dispersive X-ray Spectroscopy (EDX) showed a relatively uniform distribution of iron and zinc, indicating effective nanoparticle dispersion. Due to the inorganic nature of the nanoparticles, their increased concentration led to reductions in water solubility, moisture content, and swelling ratio by 42.7 %, 48.1 %, and 43.9 %, respectively. The electrical analysis showed that the electrical conductivity of the composite films, initially at 0.009 S·m-1 in the absence of nanoparticles, increased to 0.138 S·m-1 with the inclusion of 10 % Fe₃O₄ and 6 % ZnO. These findings highlight the potential of nanoparticle-reinforced biopolymer films for applications in active packaging and intelligent polymer systems.