Development of antimicrobial food packaging films based on electrospun polycaprolactone nanofibers encapsulating thyme oil nanoemulsions

This study developed and characterized a novel antimicrobial food packaging film fabricated from electrospun polycaprolactone (PCL) nanofibers incorporated with thyme oil nanoemulsions (TONEs). The concentration of TONEs in the film ranged from 2.5 to 15 % (v/v). The physicochemical properties, including pH, viscosity, and water absorption of the film were evaluated, with results showing favorable values (TONEs pH ≈ 5.46, viscosity ≈ 0.26 cP, contact angle ≈ 109-127 0 and water absorption ≈ 21.47 %). The microstructure of the film was observed using scanning electron microscopy (SEM), which revealed the uniform dispersion of TONEs within the PCL nanofibrous matrix, with average fiber diameters ranging from 555.68 to 571.09 nm. The TONEs interaction within the PCL matrix in the film was evaluated by Fourier-transform infrared (FTIR) spectroscopy, which revealed hydrogen-bonding interactions between thyme oil components and PCL ester groups. The antimicrobial activity of the films was assessed against common foodborne pathogens, including Escherichia coli , Salmonella enterica , Staphylococcus aureus , and Bacillus cereus . The films containing 10 % and 15 % TONEs demonstrated significant inhibition zones on agar plates (up to 25 mm for Salmonella enterica ), confirming their excellent antimicrobial efficacy, with minimum inhibitory concentrations (MICs) as low as 0.078 % (v/v) for most pathogens. The nanoemulsion formulation exhibited optimal droplet sizes (75–99 nm) and polydispersity indices (