Foaming properties and aggregation mechanism of egg white protein with different physical treatments

In this work, we studied foaming properties of egg white protein (EWP) under different physical modifications induced by supercritical carbon dioxide (SCCD), ultrasound, heat or high-pressure homogenization. Formation mechanisms of EWP aggregates and the relationships between processing parameters were discussed. Results showed that the maximum FC values were obtained via treatment with SCCD at 9 MPa (107.7%), ultrasound at 360 W (96.5%), heating at 45 °C (105%) and homogeneous pressure under 600 bar (87%), which were all dramatically higher than that of the control (29.9%). However, not all EWP treatments were conducive to the maintenance of foaming stability (FS). Results also indicated a close relationship between foaming properties and protein aggregation. Ovomucin in EWP might dissociate into small fragments or form new aggregates following treatment with SCCD, ultrasound or high-pressure homogenization, which caused a more dispersed particle size and decreased viscosity of EWP. Heating treatment greatly enhanced the viscosity of EWP, which was attributed to the irreversible destruction of the protein structure. Additionally, it seemed that SCCD maximally increased the FC of egg white through the synergy of selected pH and pressure treatments. Overall, using different physical treatments, it is possible to produce EWP with good foaming properties.