用大豆蛋白-甜菊糖苷复合稳定剂制备植物甾醇纳米乳液及其稳定性研究

Stability of Phytosterol-loaded Nanoemulsions Prepared Using Soy Protein-stevioside Complex as the Stabilizer

本研究使用大豆蛋白(Soy protein isolate,SPI)-甜菊糖苷(Steviol glycosides,STE)复合体系作为天然稳定剂制备荷载植物甾醇的纳米尺度乳液,进一步通过喷雾干燥获得油粉。油-水界面张力测试表明,STE的添加有利于快速降低油-水界面张力。乳液的粒度及稳定性分析结果显示,单独SPI稳定的新鲜乳液平均粒径为282.9nm,而添加1wt%和2wt% STE复合稳定的乳液粒径分别为217.2和193.9nm;与单独稳定的乳液相比,复合稳定的乳液在4℃下放置30d后,粒径变化较小,表明STE的添加有利于降低乳液粒度及提高贮藏稳定性。SEM图及油粉结构表征表明,单独SPI稳定的粉剂表面光滑平整,球形颗粒很少,但黏性较强;当添加STE(尤其是1wt%～2wt%)时,复合稳定的油粉无明显黏性,表面粗糙,布满了大小均匀的球形颗粒,表明植物甾醇能被很好地包埋在乳液油滴中;该分析进一步在FT-IR及XRD数据中得到证实。本研究以天然SPI-STE作为稳定剂制备的植物甾醇纳米乳液及其粉剂,这样能改善植物甾醇的水溶性,提高其生物利用度,而所得的复合稳定的油粉可用作一种新型的植物甾醇功能性食品配料。

In this study,phytosterol-loaded nanoemulsions were prepared using soy protein-stevioside complex as a natural stabilizer,and then spray-dried into oil powder.The oil-water interfacial tension measurements revealed that the addition of STE concentration is beneficial to reduce rapidly the oil-water interfacial tension.The analyses of emulsion particle size and stability showed that the average particle size of the fresh emulsions stabilized by SPI alone was 282.9 nm,while the particle size of the emulsion stabilized by SPI-1 wt%STE and SPI-2 wt%STE complexes were 217.2 and 193.9 nm,respectively.Compared with the emulsion stabilized by SPI alone,the change in the particle size of emulsions stabilized by SPI-STE was smaller after storage at 4℃for 30 days.This result suggests the addition of STE facilitated the reduction of the particle size of emulsions and improvement of their storage stability.The examinations by SEM and characterization of oil powder structure showed that the powder stabilized by SPI alone had a smooth and flat surface with few in spherical granules but relatively high viscosity.When STE(especially at 1 wt%~2 wt%)was added,the oil powders stabilized by SPI-STE complex hardly exhibited any viscosity with rough surfaces,and were covered with spherical particles of uniform size,indicating that phytosterols have been well encapsulated in the emulsion droplets.This analysis result was further confirmed by FT-IR and XRD examinations.This research used natural SPI-STE as the stabilizer to prepare phytosterol-loaded nanoemulsion and its powder,by which the water solubility and bioavailability of phytosterol have been improved,thus,phytosterol-loaded nanoemulsion stabilized by SPI-STE could be used as a novel phytosterol functional food ingredient.