Study On The Preparation And Stability Of Nanoemulsion Loaded With Phytosterols

Phytosterol?PS?is a natural substance,which has a very similar structure with cholesterol,can treat and prevent hyperlipidemia.Many clinical studies have shown that the intake of phytosterols can reduce the blood cholesterol content by 8-15%.Because phytosterol is insoluble in water and is insoluble in oil,the application in foods is largely limited.The purpose of this research is to prepare a phytosterol nanoemulsion with low surfactant useage and high embedding rate,and to explore its stability under different environments and its release in vitro.The main research contents and results are as follows:1)Construction of phytosterol nanoemulsionThe microemulsion was prepared by a spontaneous emulsification method.The formulation was obtained according to the single-phase region in the pseudo-ternary phase diagram and the dilution phase of the oil phase:surfactant=9:1,by adding water dropwise and sonicating.The droplets were reversed to prepare a nanoemulsion loaded with phytosterol.The embedding rate,K value and particle size were analysised to determine the stability of the nanoemulsion.The raw materials and process parameters of the phytosterol nanoemulsion system were optimized.The optimized preparation condition is as follows:ultrasonic power is 800 W,treatment time is 20 min,oil to water phase ratio is 1:2,and pulse mode is 4 s.The oil phase composition is ethyl butyrate and absolute ethanol,the surfactant is Tween 80,and the preparation temperature is 25°C.The prepared nanoemulsion was of oil-in-water type,the average particle size was105.34±1.70 nm,and the plant sterol embedding rate was 84.58±3.05%.2)Study on the stability of phytosterol nanoemulsionThe effects of pH,ionic strength,heat treatment and phytosterol addition on the stability of the nanoemulsion were investigated.The results showed that the stability of nanoemulsion in acidic or alkaline environment would reduce.Nanoemulsion was more stable in acidic than alkaline environment.The nanoemulsion is stable under 30-60°C after 30 minutes of heat treatment,however the stability decreases when the temperature is increased to 70°C.When ion strength increased from 0 to 100 mM,the emulsion particle size increased and the stability was reduced.When ion strength continued increasing from 100 to 500 mM,the particle size and stability were not significantly altered.When the addition of phytosterol esters increased,the stability of phytosterol esters nanoemulsion will significantly decreased.However,this phenomenos was not observed in phytosterol nanoemulsion.The compounds embedded in the nanoemulsion could affect the stability of nanoemulsion.3)In vitro simulated release of phytosterol nanoemulsion system and its kinetic equationThe release behavious of phytosterol nanoemulsion was investigated in different digestive juice,namely artificial gastric juice,duodenal juice?pH 6.0?,jejunal solution?pH 7.0?and ileal solution?pH 7.4?.The release kinetics was analysised and fitted to different equations.The results showed that the nanoemulsion was stable in artificial gastric juice,and all the five equations could not describe the release behavious.However,from the experimental results and practical applications,the residence time of the nanoemulsion in the stomach generally did not exceed 1.5h.Therefore,it does not affect the release or little effect of phytosterols.Although the pH values are different in other digestive juice,the release kinetics of phytosterol nanoemulsions is consistent with the Retger-peppas equation.The release equation in duodenal juice?pH 6.0?,jejunal solution?pH 7.0?and ileal solution?pH 7.4?was Q=22.6649 t^0.3793,Q=19.5734 t⁰.3082.3082 and Q=18.7735 t^0.3811,respectively.