植物甾醇负载的脂基纳米粒子的制备及表征

Preparation and characterization of lipid-based nanoparticles loaded by phytosterols

为扩展植物甾醇在低脂或水分散的功能食品体系中的应用,以单硬脂酸甘油酯为脂质基质,采用乳液模板法-超声联用制备了负载植物甾醇的脂基纳米粒子。通过动态光散射、高效液相、透射电镜、接触角等测定了纳米粒子的粒径和Zeta电位、包封率、微观结构以及在水中的润湿性。结果表明:所制纳米粒子呈半透明甚至透明外观,粒径为100~200 nm;超声时间4 min和快速冷却方式有利于获得粒径更小的纳米粒子;多分散指数显示纳米粒子具有良好的均一性,甚至接近单分散体系,与透射电镜观察结果一致。由于两亲性脂质基质对甾醇的相容性,纳米粒子在甾醇添加量100~500 mg时包封率均达90%以上,实现了甾醇在水中的高浓度递送。此外,冻干后的样品还表现出优异的水分散效果,在不改变性能的前提下方便了样品的储藏,为开发富含植物甾醇的功能食品或功能饮料提供了新思路。

Phytosterols is a group of natural plant-derived compounds with cholesterol-lowering and other physiological functions.However,the low solubility and low dispersion in water limit their application in the food field.In order to expand the application of phytosterols in low-fat or water-dispersed functional food systems,lipid-based nanoparticles loaded with phytosterols were prepared by emulsion template method combined with ultrasound using glyceryl monostearate as lipid matrix and lecithin as surfactant for the delivery of phytosterols in the water environment.Phytosterols loaded lipid-based nanoparticles were prepared by different ultrasonic treatment(including time and power)and cooling ways,and then the particle size,polydispersity index and Zeta potential of the obtained nanoparticles were measured by dynamic light scattering to optimize the preparation conditions.Subsequently,the effects of surfactant content and phytosterols addition on particle size,polydispersity index,Zeta potential and encapsulation efficiency of nanoparticles were studied.The encapsulation efficiency of the samples was calculated indirectly by determining the content of unencapsulated phytosterols by high performance liquid chromatography.Finally,the microstructure of nanoparticles was observed by transmission electron microscopy and the wettability of freeze-dried samples was studied by measuring the contact angle.The results showed that the samples after ultrasonic treatment showed a semi transparent or even transparent appearance,with particle size of 100-200 nm and zeta potential below-30 mV.The optimized conditions showed that the ultrasonic time of 4 min,the ultrasonic power of 120W,and rapid cooling was conducive to the preparation of phytosterols loaded nanoparticles with smaller particle size and higher negative charge.Meanwhile,polydispersity index data showed that the nanoparticles had good homogeneity,even close to monodisperse system,which was consistent with the observation results of transmission electron microscopy.Surfactant was confirmed to be an important contribution for obtaining more ideal nanoparticles.The structure of phytosterols loaded nanoparticles gradually stabilized from 0.8%of phospholipids addition,and their encapsulation efficiency reached more than 99%.Due to the compatibility of amphiphilic lipid matrix with phytosterols,the encapsulation efficiency of nanoparticles was more than 90%when 100-500 mg of phytosterols were added(the content of emulsifier was 0.8%),achieving a high concentration delivery of phytosterols in water.In addition,the freeze-dried samples also showed excellent water dispersion effect,which facilitated the storage of samples without changing the performance.The above research provides a new idea for the development of functional foods or beverages rich in phytosterols.