Preparation and characterization of ultrasound-assisted essential oil-loaded nanoemulsions stimulated pullulan-based bioactive film for strawberry fruit preservation

Ultrasound is a high-energy approach that can help with homogenization and dispersion in cavitation. In this study, nanoemulsions of curcumin and orange essential oil were prepared with ultrasound treatment at different times. The ultrasound-treated nanoemulsions for 10 min exhibited the smallest droplet size, the best storage, and higher thermal stability. The pullulan-based film with ultrasound-assisted nanoemulsions exhibited improved water vapor permeability and moisture content and the highest tensile strength and elongation at break. The structural analysis showed that ultrasonic treatment enhanced the H-bond, resulting in a more orderly molecular arrangement and intermolecular compatibility. Furthermore, the bioactive film had the maximum oil retention time. It possessed excellent bacteriostatic properties against Escherichia coli and Staphylococcus aureus due to the smallest oil droplets and uniform distribution in the film matrix. Besides, the weight loss and deterioration of the strawberry fruit were effectively reduced, thus prolonging the shelf life.