Formation of Nigella Sativa L. seed oil nanoemulsion-based delivery systems by sonication: Factors affecting particle size and stability

Due to their unique functional properties, nanoemulsions help enrich many hydrophobic compounds in water-based beverages. In this study, using two nonionic surfactants (Tween 40 and Tween 80), separately, nanoemulsions containing Nigella Sativa L. oil were prepared by ultrasound method and tested to determine their size, polydispersity index, morphology, turbidity, and stability during 60 days of storage. In this study, the type of nonionic surfactants used significantly affected the average droplet diameter in the formed systems. Hence, Tween 40 produced tiny droplets, while using Tween 80 produced larger droplets. The comparison of the mean particle sizes by the Duncan method at a 95% confidence level showed that the effect of different surfactant concentrations (2, 4, 6, and 8 wt%) on the particle size was significant. The results showed that the lowest particle size corresponding to the formulation with 4 wt% Tween 40 and the 15-min sonication was 59.2 nm, and the particle size distribution was monomodal. The results indicated that in the absence of a cosurfactant (glycerol), both pasteurization and boiling processes increased in particle size. However, adding glycerol before the thermal process improved the thermal stability of the samples. The results of this study revealed that ultrasound could be used to prepare nanoemulsions with microscopic particles in the nanometer size without high concentrations of synthetic surfactants.