Abstract: Liquid egg white was processed into instant soluble egg white powder with improved solubility by sequential ultrasonic modification and spray drying. The conditions for ultrasonic treatment were optimized using one-factor-at-a-time and orthogonal array design methods. The dispersibility, solubility and stability coefficient of egg white powder were investigated with respect to ultrasonic treatment time, ultrasonic power and egg white concentration. The results revealed that the optimal conditions were determined as 10 min, 120 W and 50% for ultrasonic treatment time, power and egg white concentration, respectively. The average dispersion time of the egg white powder produced using the optimized conditions was 56.67 s, the average solubility was 93.56 g/100 g and the average stability coefficient was 97.29%, showing good instant solubility. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis, scanning electron microscopy and particle size analysis showed that the particle size of the egg white powder obtained in this study was smaller and more uniform compared with those prepared by spray drying without ultrasonic pretreatment and by freeze drying. Circular dichroism and surface hydrophobicity results showed that the structure of proteins in the spray dried powder became disordered and the surface hydrophobicity increased after sonication, contributing to the improvement of instant solubility. The results from this study can provide a basis for the application of ultrasonic treatment in the field of new egg products.

Key words: ultrasound, egg white powder, dispersibility, solubility, stability coefficient