b. Distinctness of Yolk Shadow Outline. The distinctness of the yolk outline
or shadow outline is governed by three factors:
(1) The thickness and consistency of the albumen. The thicker the
albumen, the less distinct the outline appears, because the yolk is prevented from
moving close to the shell.
(2) Condition of the yolk. This condition is determined by the presence of
blemishes that show up before the candling light as dark shadows in the yolk, or the
absence of these blemishes; and the presence or absence of an off-colored yolk which
shows as a grayish or greenish shadow.
(3) Color of the yolk. It is difficult to determine the color of the yolk before
the candling light, except for off-color. However, extremes in yolk color may influence
the candler's judgment of the egg quality. An extremely deep-colored yolk, under some
conditions, would cast a darker shadow before the candling light than would a lighter
yolk. By concentrating on the yolk outline instead of the depth of the yolk shadow, the
grader will minimize the influence of yolk color on his quality determinations. The color
of the yolk and the firmness of the albumen are two influences that affect the
distinctness of the yolk shadow outline. Therefore, a grader cannot be even reasonably
certain which is the more important factor in any specific case. The principle of judging
distinctness of the outline rather than the depth or darkness of the shadow can be
illustrated by holding a ball close to a wall so its shadow falls on the wall, and then
holding it a little farther away from the wall. At the greater distance, the outline of the
shadow is less distinct.
c. Degrees of Distinctness. The terms used to define the three degrees of
distinctness of yolk shadow outline in the US standards of quality for shell eggs are
given below (see figure 3-5).
(1) Outline slightly defined--AA Quality. A yolk outline that is indistinctly
indicated and appears to blend into the surrounding white as the egg is twirled.
(2) Outline fairly well defined--A Quality. A yolk outline that is discernible
but not clearly outlined as the egg is twirled.
(3) Outline plainly visible--B Quality. A yolk outline that is clearly visible as a
dark shadow as the egg is twirled.