Phytochemical-loaded electrospun nanofibers as novel active edible films: Characterization and antibacterial efficiency in cheese slices

The aim of this work was to develop novel active edible electrospun coatings with antimicrobial properties through the encapsulation of essential oils (EOs) from two widely used spices (Laurus nobilis and Rosmarinus officinalis) for inactivating or reducing spoilage and pathogenic microorganisms. Firstly, EOs from dried leaves of both plants were obtained by hydrodistillation and their composition was analysed by Gas Chromatography - Mass Spectrometry (GC - MS). Interestingly, the main component in both extracts, probably as a consequence of the extraction conditions, was 1,8 cineole. Both EOs showed highest antimicrobial activity against Gram-positive than Gram-negative bacteria. Three different concentrations of the 1,8 cineole-rich EOs were incorporated within a zein matrix through electrospinning and solution properties, encapsulation yield, morphological and thermal stability of the edible coatings developed were evaluated. Then, the antibacterial efficiency of EOs-zein nanofibers (ZNF) films against Listeria monocytogenes, S. aureus and mesophilic bacteria counts (MBC) was compared with their counterparts prepared by casting (ZF) when applied directly on an inoculated side of cheese slices. EO obtained from Laurus nobilis showed higher antibacterial activity than Rosmarinus officinalis. The antibacterial effectiveness of the active films increased through storage time, showing a significant reduction of similar to 2 logarithm units of L. monocytogenes and S. aureus as compared with the control samples, after 28 days at 4 degrees C, using the highest content of 1,8 cineole-rich EOs and in films prepared by means of the electrospinning process. Interestingly, the growth of aerobic mesophilic bacteria was also inhibited in cheese slices coated with EOs-loaded ZNF based films.