Development and characterization of ethanol-free spearmint essential oil nanoemulsion for food applications using the low energy technique

Abstract

Different emulsifiable concentrates containing spearmint essential oil (SEO) were made and evaluated for their potential for giving ethanol-free nanoemulsion spontaneously upon dilution into water. Each one of these formulas had its specific composition regarding the type of excipients, surfactants, surfactant/SEO ratio and surfactant concentration. The results of this evaluation indicated that the chemical composition of SEO has a profound effect on the formation and physical stability of the nanoemulsion. The incorporation of excipients such as long chain triglyceride and propylene glycol into the emulsifiable concentrates at only 1.0% can lead to a stable nanoemulsion that resists Ostwald ripening. A particle size measurement showed that the diameter of SEO in the nanoemulsion was 28.2 nm and its nanostructure was maintained for 3 months. The application of a mixture of binary nonionic food-permitted surfactants enhanced the thermal stability of the nanoemulsion at up to 50 ᵒC. The developed ethanol-free SEO nanoemulsion has promising industrial applications in food and beverage flavoring.