Density variation in heat- and pressure-treated egg white during gel-to-glass-like transition

Simultaneous measurements of the area (volume) and mass change were carried out in heat- and pressure-treated egg white during the process of the gel-to-glass-like state transition. The calculated density of these two specimens showed quite different time variations; the density of the heat-treated specimen remained almost constant, while that of the pressure-treated one changed considerably. Moreover, the scanning electron microscopy observations revealed that the surface structure of the pressure-treated gel is larger and more coarse than that of the heat-treated one, suggesting a close relationship between the structures of the two gels and the changes in the density during the gel-to-glass-like state transition. The differences in the microscopic structures in these two gels were also elucidated by X-ray diffraction measurements.