Proteins set when they heat
Proteins are tightly folded chains. Heat unwinds them (that's denaturation), then they bond to each other and set, squeezing out some water. Egg whites start setting near 60°C (140°F). Yolks thicken near 65°C (150°F).
Overcooked protein dries out
Past the setting point, proteins keep tightening and wring out their water. That's why overcooked chicken breast is dry, fish turns chalky and scrambled eggs weep. Acid unwinds proteins too, which is why ceviche turns opaque.
Test yourself
Questions from the interactive lesson, with the answer and the why.
A raw egg white turns from clear to white in the pan. Why?
Heat unwinds the proteins and they tangle together. The tangled network scatters light, so the white looks opaque.
True or false: An egg white starts to set at a higher temperature than a yolk starts to thicken.
False. Whites begin setting near 60°C (140°F). Yolks begin thickening near 65°C (150°F).
What went wrong? You scramble eggs over high heat until they're browned. The eggs are rubbery with liquid on the plate.
The proteins tightened too far. Past the setting point, proteins squeeze out water and turn rubbery.
Fill the blank: The unwinding of proteins by heat or acid is called ___.
The unwinding of proteins by heat or acid is called denaturing. Heat or acid unfolds the protein chain, and it can then set.
At roughly what temperature does egg white begin to set?
About 60 C. Egg white starts to set around 60°C (140°F).
You want a just-set white and a soft yolk. What's the plan?
Use gentle heat and stop once the white sets. With gentle heat you can stop as soon as the white sets.
