4 BULLETIN 471, U. S. DEPARTMENT OF AGRICULTURE. 
Extended investigations at some of the agricultural experiment 
stations, in which many analyses were made of eggs from different 
kinds of hens, have shown plainly that there are no uniform varia- 
tions in the physical properties and chemical composition of brown- 
shelled as compared with white-shelled eggs. Such tests justify the 
statement that the eggs of any given breed of hens, whatever the 
color of the shells, are. on an average, as nutritious as those of an- 
other breed, provided the eggs are of the same size and freshness 
and the fowls are equally well fed. 
The color of the egg contents is also a matter of interest with 
respect to market value and domestic uses. Raw egg white has a 
more or less greenish tinge, which is apparently influenced somewhat 
by the character of the feed, though no specific coloring matter has 
been isolated from it. TVTien the albumin is coagulated by heat in 
cooking, the color varies from white to pale greenish or yellowish 
tones, hard to define, yet distinct. There is a belief that eggs with 
shells of the same color should show the same color in the cooked 
whites and that the cooked albumin of white-shelled eggs is decid- 
edly whiter than that of eggs with tinted shells. Perhaps few per- 
sons carry preferences so far as to refuse an egg because of the color 
of the white, yet it is stated on good authority that in high-class 
hotels and restaurants, where great attention is paid to details, it 
has been found that the boiled eggs served must match in color. If, 
when taken from the shell, one is greenish white and the other clear 
white, the eggs are often rejected on the ground that one of them is 
not of the required standard of excellence. 
The egg yolk owes its characteristic yellow color to a pigment 
whose chemical nature has been carefully studied. The depth of the 
yellow color apparently depends — in large measure, at least — upon 
the presence of green feed in the ration, and pale-colored yolks indi- 
cate that such feed is deficient. Though frequently the yolk is pale, 
the color which we commonly regard as a standard is a decided 
yellow, and so the pale^olked eggs are often said by housekeepers 
to be inferior, as a given number of such yolks impart to cake or 
custard less of the yellow color regarded as an indication of richness 
than do eggs of a darker yolk, a belief which chemical analysis does 
not justify. 
Although, as stated above, variations in color do not imply vari- 
ations in food value, it is not at all unlikely that there are differences 
in flavor corresponding to the color of the egg yolk, that which is 
deep yellow having a more pronounced flavor than the pale one. At 
any rate, as long as preference for deep-colored yolks and pale 
whites exists, the poultry raiser who caters to a fancy market should 
take such factors into account. 
