10 BULLETIN 565, U. S. DEPARTMENT OF AGRICULTURE. 



as unmarketable, for during shipment it is very likely to become 

 unfit for food. These eggs are difficult to grade accurately by can- 

 dling. They are of such inferior quality, however, that in case of 

 doubt they should be classed as inedible. 



The yolk sac may so weaken that the yolk seeps or strains through 

 into the white. In these eggs the yolk would appear whole before 

 the candle, but it would be weak, and the white would have a cloudy, 

 yellow color. Out of the shell the yolk will be seen to be flattened 

 and sometimes mottled and the white to be streaked with yolk. 

 Very close candling is required to detect these eggs, and since they 

 are border-line eggs, in which further deterioration is very rapid, 

 they should not be graded as marketable. 1 



The more common form of disintegration of the yolk takes place 

 through the rupture in one or more places of the yolk sac and the 

 mingling of the white and yolk. This mixing is commonly known 

 as " addling." All degrees of addling may be found, from the egg 

 in which the yolk is just beginning to mix with the white to the egg 

 in which no vestige of white is seen. The eggs representing the 

 early stage of mixing are called " mixed rots," and those representing 

 the later stage, " white rots." Both are inedible. 



Mixed rots are characterized on candling and out of the shell by 

 the irregular mixture of white and yolk. Often one portion of the 

 yolk shows more deterioration than another, a condition shown by 

 a darkened area on candling and by whitish streaks out of the shell. 

 (See PI. VI.) 



The characteristics noted for mixed rots are even more marked in 

 the white rots. In these eggs the white assumes a general yellow 

 appearance on candling and out of the shell. (See PL VII.) 



The incrusting of the yolk is a characteristic form of deterioration 

 among eggs with soiled shells which have been held in cold storage. 

 Under certain conditions the bacteria enter the shell, liquefy the 

 white, making it watery, and produce a coating or crust on the yolk. 

 Before the candle the yolk appears to have dark, mottled areas. 

 Such eggs are unfit for food. 



The position of the yolk also must be taken into consideration when 

 grading eggs by candling. In a fresh egg the 3 T olk is slightly above 

 the center in the large end of the egg. Although lighter than the 

 white, it does not float against the shell because the chalazse tend to 

 hold it in a central position in the egg. As the egg becomes stale 

 with age, and especially from exposure to heat, the white is weakened, 

 thereby making it possible for the yolk to float near the shell. This 

 condition indicates staleness if the egg shows shrinkage. 



1 An illustration of an egg with a seeping yolk is published in U. S. Dept. Agr. Bui. 224, 

 PI. XVI. 



