Self-Assembled Micelles Based on OSA-Modified Starches for Enhancing Solubility of β-Carotene: Effect of Starch Macromolecular Architecture

Self-assembled micelles based on octenyl succinic anhydride (OSA)-modified starch were prepared to enhance the solubility of β-carotene. The critical micelle concentration (CMC) was lower for OSA-modified starch with a lower molecular weight (Mw) or higher degree of substitution (DS). Above the CMC, OSA-modified starch assembled into spherical micelles with an average hydrodynamic diameter of <20 nm, as determined by dynamic light scattering (DLS). All the radii of gyration ( R_g), obtained from Guinier fitting of small-angle X-ray scattering (SAXS) data, were between 3 and 9 nm, and they were positively correlated with the Mw but negatively correlated with both the DS and the starch concentration. β-Carotene was encapsulated effectively into the starch micelles, and the concentration of β-carotene in the micelles was positively correlated with the concentration, Mw, and DS of the starch, with a maximum value of 53.14 μg/mL. The incorporation of β-carotene enlarged the hydrophobic core and induced a significant increase in the R_g of the micelles determined by SAXS, and it may have also promoted the aggregation of the micelles resulting in a marked increase in the D_h determined by DLS.