Molecular structural modification of duck egg white protein conjugates with monosaccharides for improving emulsifying capacity

Glycosylation is considered to be an effective method to improve the emulsifying property of proteins, and this work investigates and discusses the correlation between the molecular structure of glycosylated egg white protein (EWP) and its emulsifying capacity. Three types of monosaccharides, including glucose, D-galactose and mxylose, were utilized to conjugate with EWP in a wet glycosylation environment. Molecular structural properties of EWP, involving surface hydrophobicity, secondary and tertiary structures, protein flexibility, and free sulfhydryl group content, were determined. The results showed that the degree of grafting (DG), browning intensity and apparent viscosity increased significantly (P < 0.05) with the monosaccharides proportion improved, and the intrinsic fluorescence intensity and surface hydrophobicity of EWP decreased obviously during glycosylation, and the absolute value of zeta potential, protein flexibility and free sulfhydryl content improved remarkably (P < 0.05). Emulsifying capacity results showed that glycosylation improved emulsifying activity and emulsifying stability of EWP, especially after the addition of mxylose. The particle size analysis exhibited that the D-4(,3) and D-3(,2) declined obviously (P < 0.05) as DG increased. Correlation analysis revealed the improvement of the emulsifying capacity of glycosylated EWP showed in a DG-dependent manner, as remarkably influenced by molecular flexibility, surface hydrophobicity, tertiary structure changes and free sulfhydryl. The work provides a deep insight into the molecular conformation-emulsifiability relationship of EWP-monosaccharides conjugates.