Differences in the gelation, digestibility and release of antioxidant peptides of egg white/yolk in boiled eggs

In this study, the differences in the gelation, digestibility and release of antioxidant peptides of egg white (EW)/yolk (EY) in boiled eggs prepared by different boiling times were investigated. The hardness, gumminess and chewiness of boiled EW/EY both showed an increase trend with the duration of boiling time. Prolonging the boiling time increased the proportion of immobilized water in boiled EW, but reduced the retention ability of boiled EY for water or lipid. Increasing boiling time increased the content of β-sheet of boiled EW/EY at the expense of α-helix with varying degrees, accompanying with the increase of the disulfide bond and the formation of dense gel network structure. The results of in-vitro simulated digestion showed that boiled EW, especially prepared by boiling for a longer time, had a lower protein digestibility and less release of antioxidant peptides than that of boiled EY due to its compact gel network and large broken particles after digestion. This work demonstrated that prolonged boiling time will improve the gel strength of boiled EW and boiled EY, but is not conducive to their digestion and the release of antioxidant peptides.