Characterization of Oregano Essential Oil ( Origanum vulgare L. subsp. hirtum ) Particles Produced by the Novel Nano Spray Drying Technique.

Oregano essential oil (OEO), due to its wide variety of biological activities, could be a "green" alternative to chemical preservatives. On the other hand, the difficulties in its use or storage have turned researchers' interest in encapsulation strategies as a way to face stability and handling issues. Fabrication of OEO-loaded particles, using nano spray drying technique (NSD) and whey protein isolate-maltodextrin mixtures (1:1, 1:3) as wall materials appears to be a novel and promising strategy. The obtained particles were characterized in terms of volatile composition, encapsulation efficiency, and physicochemical, molecular, morphological, and antibacterial properties. The results confirmed that encapsulation of OEO using NSD achieved high levels of powder recovery (>77%) and encapsulation efficiency (>98%) while assisting in the retention of the main bioactive compounds. The partial replacement of WPI by MD significantly affected particles' physical properties. FTIR analyses revealed the possible structural stabilization of core and wall materials, while SEM verified the very fine size and spherical shape. Finally, antibacterial studies demonstrated their activity against Escherichia coli and Staphylococcus aureus , which is much stronger in comparison with that of pure OEO, proving the positive effect of NSD and particles' potential in future food applications.