Abstract
Fine structural changes in the hen's egg yolks during cooking were observed.
1) The yolk spheres of boiled egg were polyhedron similar to fresh raw yolks, and showed closely packed state, the shape of which was rounded on the outer side and slender on the inner side, and the latebra part showed the peculiar shape. The voids of the yolk spheres were narrow as compared with those of raw yolks, and the ground substrates of the yolk spheres vesiculated, and presented the state of lace. Among the protein granules existing in the ground substrates of yolk spheres those being fused and those in which the parts of low electron density arose inside the ground substrates in spotted state appeared by boiling.
2) In soft-boiled yolks, the boundaries of the yolk spheres in the middle layer and the inner layer disappeared, and the polyhedral structure was unclear. Even in fresh eggs, the protein granules distributed unevenly, and there were those that showed fusion process. The vesiculation of the ground substrates of yolk spheres was similar to that of hard boiled eggs in the outer layer part, but in the middle layer part, vesicles were partially scattered.
3) In the hard boiled yolks of stored eggs, the vesiculation of the ground substrates of yolk spheres was remarkable, and the protein granules being fused were more than those in hard boiled fresh eggs, and their distribution was uneven.
