Preparation of aqueous dispersion of β-carotene nano-composites through complex formation with starch dextrin

Aqueous dispersions of β-carotene nano-composite were prepared through a blending process with a dextrin of high amylose corn starch in immiscible phases of aqueous dextrin and organic β-carotene solutions and water solubility and stability against oxidation of β-carotene were examined. Gradual evaporation of organic solvent during the mechanical stirring allowed the formation of aqueous solutions in which β-carotene was homogeneously dispersed with dextrin. Proper control of the solid concentrations effectively induced the complex formation between dextrin and β-carotene whereas an excess amount of β-carotene (>8 mg) in a dextrin solution (200 mg in 50 mL) induced crystallization and precipitation of β-carotene. The complex particles showed an irreversible endothermic transition of V-amylose (via DSC). X-ray diffraction analysis, however, revealed that the complex had no typical V-type crystalline arrangement. Hydrodynamic size of the complex particles in the aqueous solution could be decreased to nano-scale (16–30 nm) by a mild ultrasonication. The nano-composite contained β-carotene at approximately 30% on a weight, with improved stabilities against oxidation and enzymatic digestion.