Alaska pollack ovary is sold in local markets in the frozen state, and classified as Gamuko, Mako or Mizuko by its degree of maturity.
The distribution pattern and oocyte diameter was consistent throughout the ovary and showed a homogeneous structure.
The oocyte diameter progressively increased from Gamuko, then Mako to Mizuko, indicating the mid vitellogenic, late vitellogenic, and mature stages, respectively. It was confirmed that the classification was based on the maturity level of the ovary. Gamuko had a high content of moisture and minerals and low content of lipids, and Mizuko also had a high content of moisture.
The egg membrane comprised two main layers, the outer layer and inner layer. The thickness of the outer layer slightly decreased, while that of the inner layer substantially increased with advancing ovarian maturity, and there was a substantial decrease in the transparency of the Mizuko egg membrane.
It was clarified that these changes in the egg structure were related to the physical properties and permeation of the egg.
