Study on the mechanism of interaction between mulberry anthocyanins and yeast mannoprotein

Abstract

To solve the problem of mulberry juice colour instability caused by ultraviolet radiation, we proposed the addition of mannoprotein (MP) to improve the stabilization of mulberry juice colour. First, the purified mulberry anthocyanins extracted (MAE) were identified by UFLC–MS, and their purity was determined by liquid-phase peak area normalization. The interaction mechanism between MP and MAE at different pH values was systematically investigated by Fourier transform infrared (FTIR) spectroscopy, circular dichroism (CD) spectroscopy, fluorescence spectroscopy, and molecular docking. After conjugation with MAE, the secondary structure of MP changed slightly. The fluorescence quenching of MP by MAE was dose dependent. Thermodynamic analysis showed that the main interaction forces at pH 3.2 were hydrogen bonding and van der Waals forces, while the main force at pH 7.4 was hydrophobic forces. The molecular docking results verified the good binding properties of MP with cyanidin-3-O-glucoside (C3G) and cyanidin-3-O-rutinoside (C3R).