Ultrasound-assisted phosphorylation cantaloupe seed protein isolate-curcumin complexes prepared by pH shift treatment: Structural and functional properties

The efficient loading of proteins on bioactive substances had been a research hotspot in the fields of food science and industry in recent years. The complex of ultrasound-assisted phosphorylated cantaloupe seed protein isolate (UP-CSPI) and curcumin (CUR) was prepared by pH shift method to investigate the effects of different concentrations of CUR on the structure and functional properties of UP-CSPI. The results showed that with the increase of CUR concentration, the zeta potential, the antioxidant activity and emulsifying performance of the complex improved. The interaction between CUR and UP-CSPI was a spontaneous reaction driven by Gibbs free energy (ΔG<0). The enthalpy change (ΔH) and entropy change (ΔS)>0, indicating mainly hydrophobic interaction. Furthermore, CUR caused changes in the secondary structure of the UP-CSPI, β-turns increased from 38.33 % to 45 %–47 %, random coils decreased from 25.85 % to 13 %–14 %. In conclusion, the binding of CUR to proteins through pH shift had solved the problem of CUR instability and also provided new insights for the development and application of plant protein-based delivery systems.