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human
ELI5: Why do egg-whites foam when we whisk them and do not when there is just a very tiny amount of egg yolk in it?

Why do egg-whites foam when we whisk them?

I notice when there is just a drop of egg-yolk in the egg-white bowl then no matter how long or how hard we whisk the egg-white will never foam. What does the egg-yolk do?
gpt
The foam form the whites is formed by proteins from the protein-rich egg-white. The yolk contains fats that destroy the protein foam (also called an emulsion). You can try this by mixing in a tiny amount of cooking oil into the egg-whites: it will have the same lack-of-foam effect as a tiny amount of yolk.