Nanoemulsion as an effective delivery vehicle for essential oils: Properties, formulation methods, destabilizing mechanisms and applications in agri-food sector

The growing interest in the utilization of natural plant-derived products, particularly essential oils as eco-friendly agrochemicals has spurred the consumer demand for clean-label products. Due to their robust antimicrobial and pesticidal properties, essential oils (EOs) exhibit significant potential in food preservation and agricultural applications. However, the poor aqueous stability and highly volatile nature of EOs limit their potential for practical applications in their pure form. In response, nanoemulsions (NEms) have emerged as promising delivery vehicles for EOs, offering advantages such as smaller size, high solubilization capacity, excellent encapsulation efficiency, and controlled release characteristics.

Here we review the recent advancements in the fabrication, optimization, and stability of EO NEms. The present article provides an in-depth exploration of all the currently available high-energy (ultrasonication, micro fluidization, high-pressure homogenization, rotor-stator mixer) and low-energy (spontaneous emulsification, phase inversion composition, emulsion inversion point, phase inversion temperature) methods being used for the fabrication of NEms and the respective advantages and disadvantages associated with them. Additionally, the review discusses various destabilization mechanisms such as Ostwald ripening, coalescence, etc. that generally impact essential oil NEms, providing a comprehensive understanding of the challenges associated with their stability. Furthermore, the review focuses on the recent practical applications of NEms in the sector of food preservation, flavoring agents, and sustainable agricultural practices.