Eisei Takushi

Variations of Mechanical Properties in Egg White during Gel-to-Glasslike Transition

Simultaneous measurements of weight, volume and mechanical properties have been performed during the gel-to-glasslike transition of heat-treated egg-white gel. Change in the elastic stiffness occurred in three steps: in the initial stage, it remained almost constant, then increased exponentially, and lastly, saturation was attained. The saturation point almost coincided with the characteristic time at which the rates of decrease of the weight and volume changed. In addition, from the time dependence of the differentiated values, the close correlation between the elastic stiffness and weight was revealed. It was also found that the loss of free water induces an increase of about a thousardfold in elastic stiffness of gels during transition.

Anomalous spectral properties of inhomogeneously broaded transitions of Eu3+ in Ca(PO3)2 glass

Abstract Asymmetric spectral shape of the 5D0−7F0 transition as well as anomalous emission spectra under monochromatic light excitation in Ca(PO3)2: Eu3+ are explained by taking account of broad distribution of crystal field acting on Eu3+. Energy level scheme of Eu3+ in this system and Eu3+−Eu3+ energy transfer mechanism are discussed.

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.

Solvent-Substitution Effects on Weight and Volume Changes during the Desiccation Process of Egg-White Gel

The substitution effects for ethanol and acetone were investigated by means of simultaneous measurements of weight and volume during the desiccating process of egg-white gel. The time variations of the weight and volume in ethanol- and acetone-substituted gels were much different from those in the gel without substitution; the former showed gradual decrease, while the latter showed linear time dependence approximated by two lines in the semi-log plots. The structures in the desiccated specimens substituted with ethanol or acetone were revealed, through the scanning electron microscope (SEM) and X-ray photographs to differ greatly from those prepared from the nonsubstituted gel. Moreover, in the dehydration measurements carried out after soaking the desiccated specimens in water, all of the specimens showed almost the same features as the gel without substitution.

Existence of gel-glasslike transition point in biopolymer gels

The existence of a gel-glasslike transition point in biopolymer gels such as egg-white is demonstrated with the consideration of the competitions of the free and the bound waters of gel, and a possible existence of the similar transition points are suggested for DNA gel, ribosome RNA/DNA mixtures gel, gelatin gel, agarose gel, konjak gel, and others. The time variations of the weight during the desiccation process of egg-white gel and several other gels were measured to be revealed as two or more stages. It is verified by the time domain reflectometry method (TDR) that the first and second stages are attributed to the lose of the free and bound water in the egg-white gel, respectively. The existence of gel-glasslike transition point may be a common phenomenon for materials in which the molecular network contains free and bound waters.

Simultaneous Time-Resolved Measurements of Weight and Small-Angle X-Ray Scattering of Heat- and Pressure-Treated Egg White during Gel-to-Glasslike Transition

Time-resolved measurements of weight and the small-angle X-ray scattering (SAXS) profiles of heat- and pressure-treated egg white during the gel-to-glasslike transition were performed simultaneously. Although the weight decreased with time in both types of egg whites, the Guinier radii calculated from the SAXS profiles showed quite different tendencies; in the heat-treated gel, it decreased considerably with time, but that of the pressure-treated one remained almost constant. These results indicate that the denaturation procedure considerably influences the gel structure and their semimicroscopic properties during the transition.