Preparation and physicochemical evaluation of phytosterol‐enriched sesame oil microemulsions

Abstract

Sesame oil, known for its nutritional benefits, was selected as source for phytosterol extraction. Optimal conditions of 40°C, oil‐to‐solvent ratio of 1:25, and a saponification duration of 150 min were employed to separate the phytosterols from sesame oil. The extracted phytosterols were encapsulated using microemulsion method. Various variables, such as percent of sesame oil, surfactant‐to‐cosurfactant ratio, and presence of phytosterols, were evaluated to determine their impact on particle size, polydispersity, pH, viscosity, surface tension, and stability. The particle size and PDI demonstrated significant increase with increasing oil and addition of phytosterols. A higher S:C ratio resulted in the formation of smaller microemulsion droplets. The viscosity and surface tension of the microemulsions increased significantly with an increase in the oil percent. In conclusion, the optimal composition of the microemulsion was found to be 10 wt% sesame oil with an S:C ratio of 3:1. FESEM micrographs revealed a microstructure consisting of cylindrical micelles.Practical applicationsResearch has shown that consuming 2–3 g of plant sterols and stanols can lower blood cholesterol levels by 10% and LDL levels by 15%. However, incorporating phytosterols into food products is challenging due to oxidation, insolubility, and high melting point. Most phytosterols are esterified to enrich low‐fat foods but they can be expensive and impure. The synthesis of phytosterols often involves carcinogenic chemicals and requires additional purification. Extracting phytosterols from plant sources has been proposed as a solution. However, incorporating phytosterols into food products is challenging due to their susceptibility to oxidation, particularly during processing and storage at high temperatures, their insolubility in water, and their limited solubility in fats and oils. The main aim of this study was to enrich sesame oil microemulsions with phytosterols through encapsulation. Phytosterols were extracted from sesame seed oil, followed by purification, and finally, enriched microemulsions were prepared. The optimal formulation was determined based on the evaluation of several parameters, including the mean volume diameter of particles, polydispersity index, pH, viscosity, surface tension, and physical stability.