Nisin electrospun nanofibers as promising active food packaging

Abstract

Nisin is a natural antimicrobial approved for use as biopreservative in foods. In this study, eight nanofiber formulations were manufactured by electrospinning using poly(vinyl alcohol) (PVA) or poly-ε-caprolactone (PCL) with and without nisin. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), mechanical and rheological tests were achieved to characterize the nanofibers. The assessment of antimicrobial and antioxidant activities and toxicological evaluation was also performed. The average diameter of nisin nanofibers varied between 303.6 nm and 1789.1 nm. DSC thermograms revealed typical peaks for PVA (57–65 °C) and PCL (59–64 °C), although the absence of defined signals was observed in PVA-nisin nanofibers. Incorporation of nisin caused some changes in the mechanical properties of PVA nanofibers, as the Young's modulus and elongation at break decreased from 22.9 MPa to 102.6 % to 7.65 MPa and 46.6 % respectively. The nisin nanofibers formulated with PVA inhibited Staphylococcus aureus, even when evaluated 1.5 years after manufacturing. These nanofibers were also effective against S. aureus and Listeria monocytogenes when evaluated in a milk-based food-simulating model. Using the ABTS method, nisin nanofibers showed antioxidant activity ranging from 757 to 833.67 μM TEAC. The produced nanofibers can be classified non-hemolytic materials, as all formulations presented hemolysis rate below 3 %. The PVA10 nanofibers produced with and without nisin were selected for further toxicological assessment, showing no significant effects in L929 cell viability and agar diffusion cytotoxicity test. Therefore, nisin electrospun nanofibers might be useful as active food packaging materials.