Microwave technology as a new strategy to induce structural transition and foaming properties improvement of egg white powder

Dry heat treatment is normally used to improve foaming properties of egg white powder (EWP), which actually needs long production cycle with low efficiency. In this study, microwave technology was adopted to improve the foaming properties of EWP and the relationship between structure and foaming properties of EWP was investigated. The results showed that appropriate intensity of microwave treatment could induce the transition from beta-sheet structures to alpha-helix and random coil structures. And the secondary structure of EWP after microwave treatment at 440 W for 6 min was 32.6% alpha-helix, 14.1% beta-sheet, 17.5% beta-turn and 35.8% random coil, which was similar to the structure of natural protein in egg liquid (unspray-dried). Meanwhile, the viscosity and flexibility of egg white protein were improved, which were beneficial to the protein adsorption at interface and enhancement of foam ability. Furthermore, the higher solubility and lower surface tension could be related to the fragmentation of microwave-treated egg white powder, which were helpful to the quick diffusion and adsorbance of egg white protein at interface. Therefore, the foam ability of EWP was raised to 4.84 mL/g after microwave treatment at 440 W for 6 min, having 15.3% higher than conventional dry-heat treated EWP.