Preparation And Characterization Of Starch-lutein Nanoparticles

Recently,lutein has attracted the attention of researchers because of its important physiological activity,antioxidant activity and colouration.However,lutein is not stable,and easily affected by light,high temperature and oxygen,so that to be oxidized and lose its original performance.Furthermore,its hydrophobicity makes it difficult to disperse it into water.These natures limit its applications in food,medicine and feed.To enhance stability of lutein and improve its dispersion in water are the most important problems to be solved for lutein applications.In this article,maize starch-lutein nanoparticles and amylose-lutein nanoparticles were prepared by nanoprecipitation.The lutein in the nanoparticles showed great stability to oxidant and good dispersion in water.In addition,no chemical reagents,except ethanol,was used during the preparation,which means the method is green.The average size of starch-lutein nanoparticles was between 100-400nm.It was found that most of the maize starch-lutein nanoparticles were spheres or spheroidicity with smooth surface and no breakage was observed by scanning electron microscope.But,the particle size distribution is not very uniform.Morphology of amylose-lutein nanoparticles was irregular.Starch-lutein nanoparticles were prepared with different processing parameters,such as starch concentration,lutein addition level,drying method and type of starch.The content of lutein in nanoparticles increased with the decrease of starch concentration and increase in lutein addition level.For the maize starch-lutein nanoparticles prepared with 1%?w/v,50mL?starch and 90mg lutein,lutein content was 13.2mg/g.There was more lutein in the amylose-lutein nanoparticles,prepared with 3%?w/v,50mL?amylose,than the maize starch-lutein nanoparticles under the same conditions,indicating that lutein is mainly in the form of complexes with amylose.For the amylose-lutein nanoparticles prepared with 3%?w/v,50mL?starch and 90mg lutein,lutein content was 9.82mg/g.Lutein in starch-lutein nanoparticles was oxidized by Fe³⁺?aq?.Absorbance at 446nm in UV-vis spectrum was used to characterize the extent of oxidization.The relative absorbance became 90%in 90min,while the relative absorbance of the same amount pure lutein was 60%.In other words,the oxidation rate of pure lutein is 4 times higher than that in nanoparticles.Therefore,starch-lutein nanoparticles did provide a preservation of lutein when Fe³⁺was used as an oxidant.Moreover,the amylose-lutein nanoparticles showed better preservation effect,compared with the maize starch-lutein nanoparticles.Pure lutein floated in water,while maize starch-lutein nanoparticles could form an uniform water suspension.After 24h,stratification happened,but some lutein still remained in the supernatant.The lutein content in supernatant was analyzed after centrifugation,which turned out to be 16.5 g/m L,and was 2.17 times of solubility in previous report.After 30days,there was no observable color change in supernatant and there was little sediment at the bottom,which suggested that lutein in the supernatant could keep stable for a long time.Crystalline structure,FTIR characteristics and swelling power of the starch-lutein nanoparticles were also analyzed.It was found that with increase of lutein content,swelling power increased.But there was no new infrared absorption peak,which indicated that no new chemical bond was formed.After comprehensive analysis of the starch-lutein nanoparticles,it could be concluded that lutein in the nanoparticles was mainly in the formation of complexes with amylose,and amount of lutein may also be wrapped into the nanoparticles,when starch precipitated.