Egg yolk
|
An egg yolk surrounded by the egg white. |
An
egg yolk is the part of an
egg which serves as the food source for the developing
embryo inside. The yolk together with the
germinal disc is a single
cell. The
egg yolk is suspended in the
egg white (known more formally as albumen or ovalbumin) by one or two spiral bands of tissue called the
chalaza.
As a
food, yolks are a major source of vitamins and minerals. They contain all of the egg's
fat and
cholesterol, and almost half of the
protein.
If left intact while cooking fried eggs, the yellow yolk surrounded by a flat blob of egg white creates the distinctive
sunny-side up form of the food. Mixing the two components together before frying results in the pale yellow form found in
omelettes and
scrambled eggs.
*It is sometimes
separated from the egg white and used in cooking (for
mayonnaise,
custard,
hollandaise sauce,
crème brûlée,
avgolemono, and
ovos-moles)
*It is used in painting as a component of traditional egg-
tempera*Used in producing egg-yolk agar plate useful when testing for presence of Clostridium perfringens.
The yolk makes up about 33% of the liquid weight of the egg; it contains approximately 60 calories, four times the caloric content of the egg white.
All of the fat soluble vitamins, (
A,
D,
E and
K) are found in the egg yolk. Egg yolks are one of the few foods naturally containing vitamin D. Egg yolk is a source of
lecithin, an
emulsifier.
A large yolk contains more than two-thirds of the recommended daily limit of 300mg of
cholesterol.
*
Eggs from the
Agricultural Marketing Service of the
U.S. Department of Agriculture*
Anatomy of an Egg from the
Exploratorium*
Making egg tempera from
The Society of Tempera Painters
