Investigating the physicochemical, antimicrobial and antioxidant properties of chitosan film containing zero-valent iron nanoparticles and oregano essence

The problems caused by the pollution of the environment by petroleum polymers in recent years have caused researchers to think of replacing petroleum polymers with biodegradable and natural polymers. The aim of this research was to produce composite film of chitosan (Chit)/zero-valent iron (Fe) nanoparticles/oregano essence (Ess) (Chit/Fe/Ess). Central composite design was used to study physical, morphological, antioxidant and antimicrobial properties of films. The results showed that with the increase of iron nanoparticles and oregano essence, the thickness of the film increased. The moisture, solubility and water vapor permeability of the film decreased with the increase of iron nanoparticles and oregano essence. The results of the mechanical test showed that with the increase of iron nanoparticles and oregano essence, the tensile strength and elongation at break point decreased. Iron nanoparticles and oregano essence increased significantly the antioxidant activity of the film. The results of the antimicrobial activity of the prepared films show that the addition of iron nanoparticles and oregano essence enhanced the antimicrobial activity of the film against Escherichia coli and Staphylococcus aureus. X-ray diffraction analysis showed that iron nanoparticles were physically combined with chitosan polymer. Fourier transform infrared (FTIR) results confirmed the physical presence of iron nanoparticles and oregano essence in the polymer matrix. The results of scanning electron microscopy (SEM) showed that the surface of nanocomposite films is more heterogeneous than chitosan. Iron nanoparticles and oregano essence could delay the thermal decomposition of chitosan and increase the thermal stability of chitosan film.