Молекулярная гастрономия для креативных шеф-поваров (англ. язык) - страница 165

Молекулярная гастрономия для креативных шеф-поваров (англ. язык)

Egg composition

The mass of eggs can change, but the order of magnitude (an important notion in this entire

document) is about 60 grams.

The shell makes up some grams.

The inside of the egg is composed of two main parts:

- about 50 % of the egg’s total weight is known as the white, or albumen (look, it’s yellow): about 30

grams

- about 50 % of the egg’s total weight is known as the yolk: about 30 grams.

The egg white is primarily made of proteins dissolved into water. More precisely, there are about 10

percent proteins, and 90 percent water.

It contains around 40 different proteins. The most abundant proteins are the globulins – mainly

ovalbumin and conalbumine, small coiled molecules.

The egg yolk is also composed of mainly proteins and water (50 percent), but in addition it contains

fats and cholesterol.

Yolk:

48% water

17% proteins

33% fat

White:

88% water

11% proteins

In a raw egg, the egg « white » is actually transparent. This is because all the proteins contained

within it are in their highly folded form. The individual proteins are so small that they do not interfere

much with visible light, like a wood stick in the middle of waves: if the diameter of the stick is smaller

than the wavelength, the wave goes on without much perturbance.

Effect of heating

In the presence of heat, or to a lesser extent acid and alkalis, the proteins are “denatured” and they

unwind. In this state, proteins...

turbance.

Effect of heating

In the presence of heat, or to a lesser extent acid and alkalis, the proteins are “denatured” and they

unwind. In this state, proteins can join together, or coagulate, and form a protein network, trapping the

water molecules and forming a solid gel. This is called a chemical gel, as the network is permanent

(unless, of course, you use strong chemicals in order to break the bonds between them).

The picture below shows such a network, but it does not explain why cooked egg white are white and

opaque; in reality, the edges of the network are made of many proteins, so that the size (diameter) of

these edges becomes larger than the wavelength of visible light.

Heating eggs to too high a temperature will cause some of the water contained to be squeezed out of

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