Studies on foaming and physicochemical properties of egg white during cold storage

The effects of shell egg cold storage (4 degrees C) on the foaming properties of its egg white were investigated by evaluating its physicochemical changes. The foaming ability decreased significantly (p < 0.05) while the foaming stability decreased slightly during cold storage. Specifically, the foam ability reached the minimum (25.17%) at 40 d of storage, which was decreased by 44.49% versus that at 0 d (45.33%). In the first 40 d, the decrease in foaming ability was mainly ascribed to the decreased surface hydrophobicity and the increased surface tension. Moreover, the exposed sulfhydryl groups tended to cause protein cross-linking probably by sulfhydryl-disulfide exchange reaction, leading to an increase of particle size and viscosity. However, during the 60-80 d storage, the decrease of sulfhydryl content and viscosity tended to inhibit foam formation. Additionally, more larger protein aggregates were observed with prolonging of storage period under a scanning electron microscope. This investigation reveals the change mechanisms of egg white properties during different storage periods and provides guidance for the processing of egg products.