Physical and chemical properties of β-sitosterol containing microemulsions based on sesame oil

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.