Figure 3-5. Candled appearance of the yolk.
d. Size and Shape of Yolk. The yolk in a new-laid egg is round and firm. As
the yolk ages, it absorbs water from the albumen which increases its size and causes it
to stretch and weaken the vitelline membrane and to assume a somewhat flattened
shape on top and an "out-of-round" shape generally, resembling a balloon partially filled
with water. Yolk size and shape are mentioned only in the lower quality classifications
for eggs--B and B*--where these factors become apparent. The terms used in the US
standards of quality for shell eggs to describe yolk size and shape are: enlarged and
flattened. This terminology refers to a yolk in which the yolk membranes and tissues
have weakened and moisture has been absorbed from the white to such an extent that
it appears definitely enlarged and flattened.
e. Defects and Germ Development. Relatively little is known about the exact
causes of most yolk defects other than those due to germ development. Some of the
causes which have been advanced are: irregular deposits of light and dark yolk;