Effect of change in pH, heat and ultrasound pre-treatments on binding interactions between quercetin and whey protein concentrate

The effects of change in pH, heat and ultrasound pre-treatments on the binding mechanism of quercetin (Q) with whey protein concentrate (WPC) were investigated, as well as the antioxidant capacity and stability of Q in the complexes. The main interaction between WPC and Q was hydrophobic and was not affected by pre-treatments. The binding affinity for Q with WPC at pH 7.4 after heating at 80 °C for 30 min, was the strongest, resulting in a WPC-Q complex with a more compact structure, the smallest particle size (184.43 ± 10.47 nm) and the largest ζ-potential (-20.58 ± 0.60 mV). This complex also provided the greatest stabilization of Q, when exposed to 37 °C and light. Complexation of WPC with Q reduced the ABTS radical scavenging capacity of Q, but enhanced its DPPH radical scavenging capacity and reducing power. These findings provide valuable information for optimizing the formation conditions of WPC-Q.