Improved the emulsion stability of phosvitin from hen egg yolk against different pH by the covalent attachment with dextran

Phosvitin (Pv) from hen egg yolk was conjugated to dextran (Dex) through the initial stage of Maillard reaction in an aqueous system (Pv:Dex, 1:4 (w/w); Mw of Dex, 40 kDa) at 100 °C for 6 h. The red shift of λmax occurred to Pv after the conjugation reaction from 355 to 362 nm and from 510 to 520 nm of intrinsic and extrinsic fluorescence emission spectra respectively. Circular dichroism spectra demonstrated that partial unordered secondary structure of Pv transformed into α-helix and β-turn after conjugating with Dex. The solubility of Pv–Dex conjugates represented an increase from 53.0% to 79.3% at pH 4.0. The zeta-potential of all tested emulsions decreased with lowering pH from 7.0 to 4.0. The interfacial thickness of Pv (1.0 mg/ml) absorbed onto latex particles at pH 4.0 was prominently increased by conjugation with Dex. Both the highest ESI and the slight fluctuation of D[4,3] of Pv–Dex conjugates illustrated that conjugation of Pv with Dex would be an effective method to improve its emulsion stability against more acidic pH environment.