Simultaneous nanoparticle formation and encapsulation driven by hydrophobic interaction of casein-graft-dextran and beta-carotene.

Casein-graft-dextran copolymer was produced using the Maillard reaction. The copolymer is molecularly soluble in neutral aqueous solution whereas beta-carotene is extremely insoluble. By the method of dialysis or evaporation then dispersing in water, the solubility of hydrophobic complex of casein and beta-carotene decreases whereas the solubility of dextran increases gradually, then nanoparticles formed with casein and beta-carotene core and dextran shell. The particles have spherical shape and are stable in aqueous solution against dilution, pH change, ionic strength change, FeCl3 oxidation and long time storage. The encapsulated beta-carotene can be released by pepsin or trypsin hydrolysis. To our knowledge, this is the first report of simultaneous nanoparticle formation and encapsulation induced by hydrophobic interaction. Casein-graft-dextran copolymer and the nanoparticle preparation is a green process in which only alkali and ethanol, no other chemicals, were used.