Study of physico-chemical and antioxidant properties of nanoemulsions containing cumin-lemon essential oils produced by spontaneous formation method

NEs are among the most important nano carrier systems, which are clear systems with droplet size within the range of 20-200 nm (Pezeshki et al., 2015 ).The particles smaller than the wavelength of the light are more resistant to the gravitational separation and therefore droplet aggregation compared with conventional emulsions (Pezeshki et al., 2017; Fathi et al., 2012). Also, as a promising drug delivery system they have been attracting global attention providing controlled release of active compounds (Ali et al., 2017). They are good delivery systems for lipid-soluble nutraceuticals which can be prepared by simple production methods and natural food ingredients (Hasani et al., 2015; Ozturk et al., 2015) Extensive researches have been done to use NEs for food enrichment and development of the functional foods containing bioactive components (Saberi et al., 2013, Ozturk et al., 2015, Komaiko and McClements, 2014). Formation and expansion of interfacial surface between the oil phase and the aqueous phase, requires energy input to the system and therefore these systems are thermodynamically unstable and due to various physicochemical phenomena over time they tend to separate to their constituent phases (Fathi et al., 2012; Rao & McClements, 2012; Jafari et al., 2008). This required energy could be provided by mechanical energy (high energy methods) or potential energy of its constituent components (low energy methods). Low energy methods are generally dependent to the interfacial phenomena at the boundary layer between oil and water phases and often it is more effective in small particle production compared with high energy methods ( Sagalowicz & Leser, 2008; Rao & McClements, 2012; Piorkowski & McClements, 2014). Spontaneous emulsification, one of the low energy methods in the preparation of oil in water NEs, depends on the production of very fine oil particles when an oil/hydrophilic surfactant mixture is added to the water (Pezeshki et al., 2017; Famian & Pezeshki, 2018). It is used as delivery system to encapsulate lipophilic nutraceutical components such as fat soluble vitamins Today, due to the reduction of fat in the diet and the loss of many compounds during various processes, the body is deficient in nutrients. Intrusion of hydrophobic food-drug compounds, such as various essential oils, into a variety of nanosatellite systems improves solubility and uptake into the human body and can be an effective way to enrich low-fat products. In this study, nanoamulsion containing 1: 1 ratio of subcutaneous, green-lemon oil essential oils by spontaneous formation method using spontaneous surfactant, non-hydrogen peroxide (Twin 80) and various oil phase carriers of Migliol 812, sesame oil and corn oil to surfactant ratio 15% emulsion (SER) was produced to achieve the best oil phase in the production of the optimal formulation of this nanomaterial with the smallest particle size.
NE was produced using low energy spontaneous method by addition of the oil phase drops (solution of a hydrophilic nonionic surfactant (Tween 80) to the deionized water (Pezeshki et al., 2017). The ratio of surfactant to emulsion (SER) and surfactant to oil phase (SOR) was 15% and 150%, respectively. During the formation of the emulsion the mixture is continuously stirred by the magnetic stirrer (500 rpm at 25° C). By the time when the pouring of the oil phase was completed, the systems were given stirred for 40 minutes to reach equilibrium. With regard to the effect of temperature on the particle size of nanoemulsion, a magnetic stirrer equipped with a temperature sensor (Hiedolph, Germany) was used to maintain temperature during emulsion formation.
Particle size and zeta potential measurements
The particle size and particle size distribution of system was obtained with use of a particle size analyzer (Malvern, UK) at 25°C. Measurements were performed by laser light scattering. The samples were diluted twenty times before being placed in the device and the average particle size was expressed based on volume diameter (Hamishehkar et al., 2009)
Transition electron microscopy (TEM)
The morphology of the NEs was observed using TEM (KYKY-EM3200 with an accelerating voltage of 26 kV). The drying process of the samples was conducted at room temperature on the carbon-coated grids (Klang et al., 2012).
Physical Stability
The NE formulation’s variations regarding particle size and span value as well as its physical appearance during the sixty-day storage at 25°C (on days 1, 7, 14, 30, 45 and 60th day) were studied.
Turbidity Measurements
A turbidity method was applied to specify the optical properties of the colloidal dispersions. First, with use of acidic buffer solution (pH 3.0) samples were diluted to oil concentrations ranging from 0.03 to 0.15 wt. %. The turbidity of selected samples was measured at 600 nm with use of a UV–visible spectrophotometer. The slope of a linear plot of turbidity versus oil phase concentration represents the turbidity increment (Saberi et al., 2013).

According to the results, the smallest droplet size of nanoamulsion produced with Miguel 812 (84.98 nm) carrier oil, especially dispersion (0.232), was distributed in the size of narrow and single-mode droplets. The temperature of 25 ℃ was stable. Images of the transmitting electron microscope also confirmed the particle size obtained from the particle measuring device. Transverse electron microscope images also confirmed the particle size obtained from the particle measuring device. The potential value of the optimal formulation zeta was obtained during a very small and near-zero maintenance period, and the increase in time did not show a significant effect on the change in the potential of the sample zeta. In general, using the Miguel oil phase, it is possible to produce nanomaterials containing all kinds of oily essential oils with the smallest size of droplets and stable, and then use it to enrich foods with a variety of oily essential oils.