Curcumin-loaded pea protein isolate-high methoxyl pectin complexes induced by calcium ions: Characterization, stability and in vitro digestibility

In the present study, curcumin-loaded pea protein isolate-high methoxyl pectin complexes (Cur-loaded PPI-HMP complexes) were first fabricated at neutral pH via the induction of calcium ions (Ca2+). The influence of different concentrations of Ca2+ (from 0 to 48 mmol/L) on the properties and formation mechanism of the complexes was investigated. The results showed that particle size and morphology of Cur-loaded PPI-HMP complexes were affected by the concentration of Ca2+. The zeta potential and Fourier transform infrared spectroscopy revealed that electrostatic interaction was the main force involved in Ca2+ bridge formation. The electrical conductivity of complex dispersions revealed that the maximum concentration of Ca2+ binding to PPI was 24 mmol/L. The encapsulation efficiency of Cur in the complexes was greatly increased to 97.33 ± 0.05% at Ca2+ concentration of 24 mmol/L, and the stability of Cur in the complexes against UV light and thermal stress was also significantly improved. The XRD showed that the redundant Ca2+ could cause the dissociation of Cur from the complexes and existed in the crystalline state. Moreover, the PPI-Cur-HMP-Ca2+ complexes could also delay the release of Cur in the simulated gastrointestinal tract.