Optimization of antimicrobial and antioxidant film of gluten containing Heracleum persicum essential oil, magnesium oxide nanoparticles and polypyrrole by Response Surface Methodology

The aim of this study was to prepare antimicrobial and antioxidant films based on wheat gluten and Heracleum persicum essential oil, magnesium oxide nanoparticles and polypyrrole were used to improve the structure of films. Response surface statistical design was used to investigate the effect of the essence, magnesium oxide nanoparticles and polypyrrole on the physicochemical properties of the films. According to the obtained results, moisture absorption, solubility and water vapor permeability of the films decreased with increasing the content of essential oil and pyrrole. Increasing the amount of essential oil and pyrrole in the film structure improved the mechanical properties of the films. Then, the optimal films (containing 12% essential oil, 0.904% magnesium oxide and 0.2 pyrrole) were studied to evaluate the structural and antimicrobial properties. The antibacterial, antioxidant and electrical conductivity of the film was greatly increased in the presence of all three additives of essence, magnesium oxide nanoparticles and polypyrrole (P <0.05). Gluten-essence-MgO-PPy (Glu-E-MgO-PPy) composite film had the highest antioxidant and antibacterial properties. The optimal film had higher antibacterial activity against Escherichia Coli ATCC13706 compared with Staphylococcus aureus ATCC6538. SEM images showed that the essence and polypyrrole strengthened the gluten film structure and made it more resistant to the passage of water vapor. FTIR spectra confirmed the electrostatic interactions between gluten and essence and polypyrrole. The results of thermal analysis showed that polypyrrole greatly increased the thermal resistance of the film and the nanoparticles had little effect on the thermal resistance. The results of this study showed that composite and bioactive film with three important properties of electrical conductivity, antibacterial and antioxidant has the potential to be used as an active and intelligent film in the packaging of perishable food products.