Formation and characterization of the binary complex between zein and propylene glycol alginate at neutral pH

The effects of propylene glycol alginate (PGA) at different concentrations on the physical, conformational, thermal and morphological characteristics of zein particles were explored at pH 7.0. Results showed that the size of zein particles increased from nano-scale to micron-scale with the increasing proportion of PGA incorporation, consequently leading to greatly raised turbidity of zein colloidal dispersions. There was a large increase in fluorescence intensity of zein in the presence of PGA, indicating conformational change of zein. Results of X-ray diffraction and Fourier transform infrared spectroscopy revealed that the binary complex between zein and PGA was successfully generated due to the non-covalent interaction forces, mainly including hydrogen bonds and hydrophobic effects. The presence of PGA enhanced the physical and thermal stability of zein colloidal particles. The clumps and irregularly-shaped aggregates with large diameters were observed after the interaction between zein and PGA at mass ratios of 2:1 and 1:1. Findings in this work may help further understand the interaction theory between negatively charged proteins and polysaccharides and provide new insights into for the development of potential carriers for bioactive compounds in food system. (C) 2016 Elsevier Ltd. All rights reserved.