Fabrication and characterization of binary composite nanoparticles between zein and shellac by anti-solvent co-precipitation

The anti-solvent co-precipitation method was applied to fabricate zein (Z) and shellac (S) composite nanoparticles with different mass ratios (Z:S, 50:1, 10:1, 5:1, 2.5:1, 1:1, 1:1.5 and 1:2.5) at pH 8.0. Measurement of particle size and turbidity, in combination with analyses of Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), differential scanning calorimetry (DSC), fluorescence spectroscopy, and atomic force microscope (AFM) were performed to characterize Z-S composite nanoparticles. Results showed that hydrogen bonding and hydrophobic attraction were involved in the interactions between zein and shellac, leading to the changes in secondary structure and thermal stability of zein. At low levels of shellac (Z:S, from 50:1 to 2.5:1), a compact structure of Z-S composite nanoparticles was formed, which had smaller particle sizes, higher turbidity value and better thermal stability. At high levels of shellac (Z:S, from 2.5:1 to 1:2.5), a cross-linked structure of Z-S composite nanoparticles was generated, which exhibited larger particle sizes, lower turbidity value, and poorer thermal stability. The potential mechanism of a two-step process was proposed to explain the formation of Z-S composite nanoparticles. Findings in the present work will help further understand the interaction between alcohol-soluble biopolymers (e.g. zein and shellac) and provide a new insight into the development of potential carriers for bioactive compounds. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.