Impact of pH on the interaction between soy whey protein and gum arabic at oil–water interface: Structural, emulsifying, and rheological properties

Abstract

In this study, gum arabic (GA) and pH modulation were used to change the structural and emulsion properties of soy whey protein (SWP). The interaction mode and binding site of SWP and GA were analyzed by structural characterization and molecular modeling techniques. The microscopic morphological, emulsifying, interfacial, and rheological properties of emulsions formed by SWP–GA complexes were characterized. The ζ-potential results showed that pH has a significant effect on the electrostatic interaction between SWP and GA. Fluorescence spectra and surface hydrophobicity (H0) illustrated that the H0 of SWP–GA complexes significantly decreased. Fourier transform infrared spectroscopy (FTIR) showed that GA provided the basis for the formation of ordered structures and that the β-sheet content of SWP–GA complexes reached the maximum value (44.68%) at pH 6.0. Molecular docking results further verified that SWP–GA interaction occurred through hydrogen bond and hydrophobic interaction. Compared with SWP emulsions, droplets of SWP–GA emulsions were uniformly distributed and formed a dense network structure. The emulsifying activity index and emulsifying stability index significantly improved, especially at pH 6.0, which were 902.78 ± 4.44 m2/g and 4648.27 ± 203.59%, respectively. SWP–GA complexes facilitated adsorption at the oil–water interface and reduced the interfacial tension. GA significantly improved the rheological properties of SWP–GA emulsion. Furthermore, statistical analysis indicated that the structural properties of SWP–GA complexes were significantly correlated with the emulsifying and interfacial properties of SWP–GA emulsions. This study would provide theoretical guidance for the preparation of the stable emulsion system of protein–polysaccharide complexes.