---

In recent years, phytosterols have been widely used as an additive in foods to regulation cholesterol level in the plasma, in cosmetics and pharmaceuticals. The high melting point and insolubility in water and oil make it difficult to add phytosterols to food. In this study, microemulsion containing β-sitosterol with different formulations were prepared from sesame oil and tween 80 as surfactant and a mixture of ethanol/propylene glycol as cosurfactant; An ultrasonic homogenizer was used to reduce the particle size. Oil percentage and the ratio of surfactant: cosurfactant was changed in the samples to obtain an optimal formulation. The mean particle diameter was about 50 nm and lower. There was no significant relationship between β-sitosterol containing, mean diameter and polydispersity index of microemulsions (p>0.05). The mean particle diameter was increased when oil content and the ratio of surfactant: cosurfactant increased (p<0.05). Poly dispersity index of the samples were below 0.5. The viscosity and surface tension of the samples increased with the increase in oil content and β-sitosterol addition (p <0.05). The stability of the samples was also predicted at various temperatures. The best results were obtained for the sample containing 40% oil, with a surfactant: cosurfactant ratio of 2:1, and the addition of β-sitosterol did not have an adverse effect on the results.

---

Among the main problems in fortifying foods with phytosterols are their high melting point, gypsum taste and low solubility. One of the ways to overcome these problems is to use a suitable coating material and phytosterol coating. . In this study, olive oil was used for phytosterol coating due to its high nutritional benefits by nanoemulsification method. In order to optimize the underlying conditions, the percentage of olive oil (oil phase), the percentage of sodium dodecyl sulfate (surfactant) and gelatin (as stabilizer) were considered as independent variables and the particle size was considered as the response. Experimental conditions were determined by designing the experiment using the mini-tab software using the RMS response surface methodology and using the Box-Behnken design. Two formulations (7.1, 3.7, 90) and (7.9, 3.7, 80) due to having the smallest particle size (103-105) nm as suitable and experimental nanoemulsification conditions for Encapsulation Phytosterols were selected. The results after coating showed that the particle size, pH, viscosity, surface tension and physical stability of these nanoemulsions provided the best conditions for their application. Finally, the formulation (7.1, 3.7, 90) after Encapsulation was selected as the best formulation for phytosterol Encapsulation due to its suitable physical and chemical properties, greater stability and 112 nm particle size.