the network; at any temperature, water evaporates (this is why ponds dry at the shining sun, but even
roads are finally dry, after the rain), but if temperature is higher than 100°C, then water boils and forms
craters in egg white.
In conclusion, over-cooking an egg white therefore makes it rubbery for reasons clearly explained in
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Water molecules being squeezed out of a tightly bonded protein network
Presence of salt
In cooking, eggs are usually salted. As well as providing a taste advantage, the Na+ and Cl- ions
present in the salt will surrounded the positively and negatively charged regions of the proteins,
neutralising them and thus reducing repulsion between similarly charged regions on neighbouring
This causes the egg proteins to coagulate more quickly and at lower temperatures. In addition, the
proteins involved in the network can not get as close to each other as they would normally (due to the
presence of the surrounding ions) so the resulting network is also tenderer and less tough.
Presence of acid
When an acid is added to egg white, there are some effects, but not immediately. Acids are
compounds that give hydrogen ions (H+).
In the presence of these H+ ions, both denaturation and coagulation of proteins is increased because
acids increase the unwinding of the proteins, and allows them to form a network. More precisely, parts
of proteins get the same electrical charge, so that they repel themselves: proteins unwind. And
unwinding gives way to coagulation.
H+ H+ H+
Effect of different temperatures
The coagulation of egg white proteins begins at temperatures a temperature of 62°. At higher
temperatures, as more and more proteins denaturate and contribute to the network, the consistency of
the cooked egg white is more and more firm.
More precisely, the denaturation temperatures of egg white proteins are:
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Proteins Denaturation temperature
For the yolk :
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