Impact of ultrasound treatment on the foaming and physicochemical properties of egg white during cold storage

The effects of ultrasonic treatment (180 W, 25 min) on the foaming and physicochemical properties of egg white from shell egg stored for seven periods (0, 15, 30, 45, 60, 75 and 90 d) were investigated in this study. The foaming ability significantly increased after ultrasound treatment and the highest foaming ability (99.13%) was achieved at 60 d compared to untreated egg white (29.75%). This improvement was ascribed to the increased free sulfhydryl content and surface hydrophobicity, indicating that egg white protein became easier to adsorb at the air-water interface and its structure was more flexible. However, a reduction in the foaming stability of ultrasound-treated egg white resulted from the lower absolute zeta potential. Moreover, decreasing particle size and broadening protein size distribution were obtained after ultrasonic processing. Using scanning electron microscopy, small aggregates were observed on the surface of the untreated sample after storage, while the ultrasound-treated sample had large numbers of irregular and unevenly distributed pores with different sizes. These results provide important evidence of the protein properties induced by ultrasound modification during storage, and further expand the ultrasound application in the food storage industry.