Entrapment of curcumin in whey protein isolate and zein composite nanoparticles using pH-driven method

In this study, encapsulation strategy of curcumin was employed by fabricating protein-based composite nanoparticles with hydrophilic whey protein isolate (WPI) and hydrophobic zein using an alcohol-free pH-driven method. The mass ratio of WPI to zein had a great effect on WPI and zein composite properties. At the WPI to zein mass ratio of 8:2, the resulting composite nanoparticles showed a relatively small size (about 90 nm). The composite nanoparticles significantly enhanced the solubility of curcumin to be above 0.65 mg/mL and exhibited desirable storage and physical stability as well as re-dispersibility. The presence of zein significantly improved thermal stability of the composite nanoparticles and the retention rate of curcumin at a high temperature (80 °C) compared to single WPI only. X-ray diffraction confirmed that curcumin was present in an amorphous state inside the nanoparticles. Fourier transform infrared analysis revealed that hydrophobic attraction and hydrogen bonding were the major forces involved in the formation of the composite nanoparticles. Both the pH-potential curve and the transmission electron microscope images revealed that the composite nanoparticles had a core-shell structure with the zein core and WPI shell. The formation mechanism of the composite nanoparticles was also proposed. The composite nanoparticles fabricated by the simple, safe and cost-effective pH-driven method interpreted the potential for delivery of curcumin.