Microfibrillated cellulose addition improved the physicochemical and bioactive properties of biodegradable films based on soy protein and clove essential oil

Abstract

Active nanocomposite films based on soy protein isolates (SPI), microfibrillated cellulose (MFC) and clove essential oil (CEO) were developed, and the contribution of each component to the functionality of ensuing films was intended to elucidate. MFC with diameters of 50-60 nm, an average length of 485 ± 2 μm, a high aspect ratio of 8800 and 35.5% of cristalinity, was prepared from Phormium tenax fibers by mechanical treatment. Films were processed by casting from aqueous dispersions containing SPI, glycerol (as plasticizer), different MFC contents and the optional addition of CEO. All filmogenic dispersions exhibited a pseudoplastic flow behavior and formed homogeneous films. The addition of MFC reinforced the protein matrix, increasing the mechanical strength and Young´s modulus of the films and improving their barrier properties to water vapour and oxygen. On the other hand, the addition of CEO caused some plastification effect of protein and nanocomposite matrix (mainly observed in the mechanical properties, solubility and water content) and a differential modification in the barrier properties, as the oxygen permeability increased and WVP decreased. Furthermore, it conferred important antioxidant properties and antimicrobial activity against bacteria related to foodborne diseases that increased with increasing MFC content in the formulation. Nanofibers seemed to favor the release of the active compounds of CEO probably due to the improved dispersion of CEO in nanocomposites through a higher amount of smaller droplets. These active nanocomposite films with antimicrobial and antioxidant properties are promising for the development of active food packaging.