Why does egg white turn white when cooked?
What's changing is the protein inside the egg white.Raw egg white is clear because its proteins float in the water curled up into tiny balls, so light passes through. When heated, the proteins unfold and tangle together, forming a mesh that traps water. This mesh blocks light, so the egg white looks white, and at the same time it changes from a liquid to a solid. Egg white starts to turn cloudy at about 60℃ and becomes white and opaque at about 65℃.
Raw egg white: water and protein
According to an explanation from North Carolina State University, egg white is mostly water, with dozens of kinds of proteins in it. In a raw egg, the proteins float in the water shaped like tiny balls of curled-up thread, so light passes through and the egg white looks clear.
Heat unfolds and tangles the proteins
The Exploratorium, a science museum in the United States, explains that when egg white is heated, the proteins move around wildly, and the weak bonds that kept them curled up break. The unfolded proteins then form new bonds with each other, making a mesh that holds the surrounding water.
Turning white and firm at about 65℃
According to food safety researchers at North Carolina State University, egg white starts to turn cloudy at about 60℃, and at about 65℃ it becomes opaque and no longer lets light through. The same change turns the egg white from a liquid into a solid. The yolk starts to set at about 70℃, a higher temperature than the white.
The temperatures are from North Carolina State University's explanation, as in the text.
Overcooking makes it tough
If eggs are heated at a high temperature for too long, too many bonds form between the proteins, and the egg white becomes hard and rubbery. How firm the white and yolk become depends on cooking time and heat, because these change how the protein mesh forms.
Want to know more?
- When you whip egg whites into meringue, the proteins that touch the air unfold and link together, which keeps the bubbles in place.
- Egg yolk contains a substance that helps oil and water mix, which is essential for making mayonnaise.
Quick quiz: test yourself
Why does egg white turn white when cooked?
Show the answer
- The surface gets burnt
- Proteins form a tangled mesh
- Air bubbles get mixed in
Proteins form a tangled mesh Heat makes the proteins unfold and tangle together into a mesh that traps water. This mesh blocks light, so the egg white looks white.
Heat makes the proteins unfold and tangle together into a mesh that traps water. This mesh blocks light, so the egg white looks white.
Next quiz ›Sources
- Why Do Egg Whites Turn White When You Cook Them?NC State University News
- Science of EggsExploratorium
This article was written after checking the sources above as of 2026-10-03. Explanations may change as research progresses. Photo credits are shown below each photo.
