Molecular characteristics and foaming properties of ovalbumin-pullulan conjugates through the Maillard reaction

The aim of this research was to synthesize ovalbumin-pullulan conjugates through the Maillard reaction and compare the molecular characteristics of native ovalbumin (N-OVA), heated ovalbumin (H-OVA) and glycosylated ovalbumin (G-OVA). The glycosylation was monitored by the degree of graft and Amadori compound. Covalent binding between ovalbumin and pullulan was confirmed by SDS-PAGE and FTIR. CD spectra showed that glycosylation could inhibit the heat-induced formation of beta-sheet. Due to the shielding effect of polysaccharide, H-0 and fluorescence intensity of G-OVA were lower than those of heated group. Meanwhile, zeta potential values of G-OVA at three different pH were extreme small, close to zero. Compare with N-OVA, the free exposed sulfhydryl contents of conjugates increased and total free sulfhydryl contents decreased. For G-OVA, foaming stability was 50.5%, which was a factor of 7.1 higher than the value of N-OVA (7.1%). G-OVA foam displayed smaller and more homogeneous bubble size than N-OVA and H-OVA. In addition, G-OVA foam presented the slowest rate of the bubble size increase over time. Overall, Maillard reaction was proven to be successful in enhancing the foaming properties of ovalbumin.