Environmental stress-induced conformational transitions modulate foaming and gelation properties of glycosylated egg white proteins

Glycosylation induces covalent grafting, resulting in conformational shifts that modulate the functional properties of proteins. This study examines the effect of conformational changes on the foaming and gelation properties of d-xylose glycosylated egg white protein (G-EWP) under different pH, ionic strength, and temperature conditions. Glycosylation end-product content increases initially, then reduces with increasing temperature while negatively correlating with pH and NaCl concentration. Treatment with NaCl induces electrostatic shielding on the G-EWP surface, decreasing the absolute value of ζ-potential from 19.63 mV to 14.9 mV. Temperature promotes thermal denaturation and macromolecular aggregation of G-EWP, increasing the particle size significantly from 523.9 nm to 4458.92 nm. Spectroscopic and protein structure analyses show that different environmental stresses alter the conformational structure of G-EWP, causing the rearrangement of amino acid residues. High temperature exerts a more pronounced effect on the secondary structure of G-EWP compared to variations in pH and NaCl, where the α-helices decline from 40.37% to 7.83% and the β-turns content increases from 19.30% to 39.57%. Reheating at 60 °C and acid treatment significantly increases the gel hardness, and the foaming capacity of G-EWP declines gradually with increasing pH and NaCl concentration, but improves with increasing temperature. Correlation analysis reveals that the molecular flexibility, β-sheet and β-turn effectiveness regulate the foaming capacity, and the charge variation positively modulates the gel properties of G-EWP.This study provides insight into regulating the functional properties of G-EWP effectively in industrial applications.