Egg yolk peptide-iron chelate: preparation, conformational structure, chelating mechanism and stability in vitro

Abstract In this study, a method to produce iron-chelating peptides derived from egg yolk proteins was developed and optimised. The egg yolk proteins were enzymolysed and ultrafiltered to prepare egg yolk peptide (EYP), and then the EYP was chelated with Fe to produce egg yolk peptide-Fe (EYP-Fe). The optimised mass ratio of peptide to iron, pH, temperature and reaction time were found at 8:1, pH 8.0, 40 °C and 30 min, respectively. The mean particle size of EYP-Fe was 389.2 ± 2.61 nm, and the chelating ratio was 95.38 ± 1.93%. The measurements of FTIR, X-ray photoelectron spectroscopy (XPS) and NMR showed that ferrous ions mainly combined with the amino and carboxyl of EYP to form EYP-Fe. In vitro stability studies have shown that the iron release rate of the EYP-Fe is maintained at around 5% under alkaline conditions, and there is no significant difference in iron release rate under conditions of 30 °C–80 °C; besides, it has a lower iron release rate (18%) in gastrointestinal digestion compared to FeSO4 (97.93%), indicating that the EYP-Fe has good heat tolerance, alkalinity and digestion tolerance. The above results provide a scientific basis for the use of EYP-Fe derived from egg yolk protein as a potential alternative to iron supplements.