4 BULLETIN 471, U. S. DEPARTMENT OF AGEICULTUBE. 



Extended investigations at some of the agricultural experiment 

 stations, in which many analyses were made of eggs from different 

 kinds of hens, have shown plainty 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. Eaw 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. When 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-yolked 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. 



