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Experimentbeginnerdraft

Egg whites with and without fat

Also searched as: egg white experiment, why won't egg whites stiffen

In short: A tiny drop of egg yolk stops egg whites from whipping stiff.

Picture it

Like blowing soap bubbles with greasy fingers: a little fat, and no bubble holds.

Before · Afteregg white
no fat
a drop of yolk
Schematic
You need · 10 minutes
  • 2 egg whites
  • a drop of egg yolk or oil
  • two clean bowls
  • whisk or hand mixer

How it’s done

Sequence · Step 1 of 4
1234

Put one egg white in each bowl.

All steps as a list
  1. Put one egg white in each bowl.
  2. Add a tiny drop of egg yolk or oil to one bowl.
  3. Whisk both for the same length of time.
  4. Compare.

What you see

Without fat you get stiff, glossy whites. With the drop of fat it stays runny or soft and foamy.

Why it happens

The proteins form a skin around the air bubbles. Fat pushes in between, and the bubbles burst.

Related entries
Foams and whipping in airEgg whites won't whip stiffWhipping (egg whites, cream)
Sources · 1
  • Harold McGee: On Food and Cooking (2004)