Antifungal activity of combined treatments of active methylcellulose-based films containing encapsulated nanoemulsion of essential oils and γ–irradiation: in vitro and in situ evaluations

Abstract : Microfluidization was used to develop methyl cellulose (MC)/cellulose nanocrystal CNC based nanocomposite films containing a plant essential oil (EO) blend (oregano: thyme) emulsion. A three factorial experimental design was used to systematically optimize the microfluidization pressure based on size and antifungal activity of the prepared emulsion. Results showed that microfluidization of the film forming dispersions provide a novel approach for the development of high strength bionanocomposite films. Incorporation of 7.5% CNC into MC containing 0.50–0.75% EO and application of a pressure of 15 k psi (103 MPa) created a nanoemulsion with particle size ≤ 100 nm which exhibited significant antifungal activity in vitro against Aspergillus niger, A. flavus, A. parasiticus and P. chrysogenum. In situ tests with MC/CNC based bioactive films containing EO emulsion produced a 2 log reduction in fungal growth in infected rice during 8 weeks of storage at 28 °C. Methyl cellulose nanocomposite films containing EOs nanoemulsion showed a slow release (35%) of volatile component over 12 weeks of storage period. The addition of CNC as reinforcing filler improved the tensile strength of the MC based films by 30% and decreased water barrier and release properties by 9 and 25% respectively. In addition, combined treatment of bioactive films with an irradiation treatment at 750 Gy showed more pronounced antifungal and mechanical properties than treatment with the bioactive film or irradiation alone. These results show the potential for EO-loaded methyl cellulose-based films to prolong shelf life of food products.