Fabrication, characterization and mechanistic exploration of zein/pectin binary nanocomplex by a one-step and organic solvent free technique

Previous studies have shown that the organic solvent-free method has considerable potential for delivery systems in food applications. In this study, Nanocomplex of zein and pectin from apple (AP) or citrus (CP) was systemically fabricated and characterized by adjusting pectin pH (2.0–11.0) and mass ratios of zein:pectin (1:0, 1:0.5, 1:1, 1:2 and 1:3) via one-step pH-shifted process. Results showed that the size of zein/pectin nanocomplex remarkably decreased from >500 nm to ∼150 nm with the increasing pH level of pectin solution and proportion of pectin addition. Spherical shape was observed for nanocomplex formed by AP and CP in transmission electron microscopy images. Compared with zein/AP nanocomplex , zein/CP nanocomplex exhibited the smaller size, smoother surface and lower surface hydrophobicity, prompting us to conclude that CP, as compared to AP, had better performance. To further explore the mechanism, the behavior difference could be interpreted by the altered hydrophobic interaction between zein and pectin as revealed by fluorescence spectroscopy and Fourier transform infrared spectroscopy (FTIR). Findings in this study would facilitate the understanding of interaction between zein and pectin and provide new perspectives of pH-shift induced zein nanocomplex.