Effect of NaCl on thermal aggregation of egg white proteins from duck egg

Thermal aggregation of duck egg white solution (1 mg protein/ml, pH 7) was monitored in the presence of different NaCl concentrations (0–6%, w/w) across the temperature range of 20–90 °C. Duck egg white solution exhibited higher turbidity with coincidental increases in surface hydrophobicity and decreases in sulfhydryl group content as temperatures increased from 70 to 90 °C (p < 0.05). As NaCl concentration increased, the negative charge decreased, with coincidental increases in particle size of aggregate after heating to 90 °C. As visualised by confocal laser scanning microscopy, larger clusters of protein aggregates were observed with increasing NaCl concentrations. Major duck egg white protein with molecular mass of 45 kDa disappeared in the presence of 2–6% NaCl after heating above 80 °C, regardless of concentrations. Therefore, NaCl, especially at high concentrations, could induce thermal aggregation of duck egg white protein, which could determine the characteristics of salted egg white after heating.