Changes in the Ultrastructure of Egg Yolk by the Growth of Streptococcus faecalis var liquefaciens

The growth of Streptococcus faecalis var liquefaciens caused the separation of egg yolk into upper and lower layers. Ultrastructure studies using transmission election microscopy showed that the upper layer was mostly low density fraction (LDF) with few electron dense particles. In contrast, the lower layer was mostly high density fraction (HDF). The separation factor caused aggregation of the HDF and openness of the structure of the matrix. The extent of incubation had a pronounced effect on the ultrastructure. Freeze-thaw treatment produced greater aggregation of HDF and more disruption of the LDF matrix, particularly in the lower layer.