Improving rehydration of egg white powder through modifying its physicochemistry properties by ultrasound-assisted glutaminase deamidation

Poor rehydration is one of the limiting factors affecting the processing and functional properties of egg white powder (EWP). In order to improve rehydration, this study explored the ultrasound-assisted deamidation method (ultrasound power: 100 W, 200 W, 300 W, 400 W and 500 W) and its effects on the physicochemistry and processing properties of EWP. The degree of deamidation increased at first and then decreased with the increase of ultrasound power. After deamidation, rehydration significantly increased. SDS-PAGE results showed that glutaminase had no obvious effect on protein composition. However, circular dichroism spectroscopy, Fourier transform infrared spectroscopy and surface hydrophobicity analyses showed that deamidation contributed to the decrease in α-helix and increase in random coil structure, which generated more flexible and stretchable conformational proteins. The average particle size and ζ-potential of EWP changed significantly, indicating that ultrasound-assisted deamidation treatment caused the de-aggregation and re-aggregation of EWP. These helped to promote the wettability, solubility and dispersion and reduce the turbidity of the rehydrated solution by altering the surface hydrophobicity and increasing the flexibility of EWP molecules. Best rehydration was observed in the sample of 300 W-EWP. These results suggested that ultrasound-assisted deamidation treatment is a practical method to enhance the processability and applicability of EWP.