Soybean β-Conglycinin Nanoparticles for delivery of hydrophobic nutraceuticals

Abstract

We report the formation of nanoparticles using soybean β-conglycinin (β-CG), a globular storage protein, to encapsulate vitamin D (VD), as a model hydrophobic nutraceutical for food fortification applications. VD-β-CG nanoparticles were formed in phosphate buffer, at both pH 6.8 and pH 2.5, by drop-wise addition of ethanol-dissolved VD to β-CG solution at room temperature, while vortexing. Turbidity measurements of the nanoparticle solutions showed optical clarity compared to VD in phosphate buffer which, in the absence of β-CG, formed suspensions whose turbidity increased almost linearly with vitamin concentration. Dynamic light scattering measurements revealed that while VD in buffer formed particles with a mean diameter of ~600 nm, the VD-β-CG nanoparticles had mean diameters in the 50–400 nm range. β-CG also protected VD from several forms of degradation: After exposure to 70 °C for 30 s at pH 2.5, VD was reduced by 75 % whereas the VD-β-CG nanoparticles lost only 2.5 % of their vitamin content. At the end of a three week shelf life test, nanoparticles retained 70 % and 90 % of their vitamin content at pH 6.8 and 2.5, respectively, whereas the protein-free controls retained only about 13–22 % (with no significant difference between retention at these two pH values). After two hours of simulated gastric digestion, the nanoparticles retained over 90 % of their vitamin content, whereas protein-free controls retained only ~50 % of their vitamin content. These results highlight the potential of β-CG as a nanoencapsulation agent for hydrophobic nutraceuticals for enrichment of food and beverages, including clear ones.