The effect of pH on structural properties and interaction mechanisms of zein/epicatechin gallate complexes.

This study aimed to investigate the effects of pH on the structural properties and interaction mechanisms of zein/epicatechin gallate (ECG) complexes. QCM-D data demonstrated that the binding capacity of ECG to zein was significantly higher under alkaline condition (pH 9) compared to neutral and acidic conditions (p < 0.05). Molecular docking analysis revealed that the formation of zein/ECG complexes was primarily driven by hydrogen bonds, van der Waals forces, and hydrophobic interactions. Fourier transform infrared spectroscopy indicated changes in secondary structure of zein. Additionally, these structural changes resulted in a decrease in content of free sulfhydryl groups while increasing solubility and antioxidant activity. Furthermore, melting temperature of zein/ECG complexes decreased after treatments at pH 3, 5, and 9, while it increased at pH 1 and 7. These findings underscore the significance of pH in ECG and zein interaction, offering valuable insights for the development of zein/ECG complexes as food additives.