The cleanest way to separate egg white from yolk is to crack the egg on a flat surface, split the shell in two, and pass the yolk back and forth between the halves, letting the white slip through your fingers or into a bowl. When whipping the white to stiff peaks, the most critical point is that the bowl and whisk are completely free of fat, since even a trace of oil stops the white from ever gaining volume.
How do you cleanly separate white from yolk?
Passing the yolk back and forth between the shell halves is the classic method, but the shell's sharp edges can easily pierce the yolk membrane; cracking the egg into a clean bowl and separating the yolk by hand or with a funnel gives a safer result. If the yolk membrane tears and mixes into the white, that white will struggle to whip to stiff peaks; if separating several eggs, cracking each one into its own small bowl before adding it to the main bowl means one mistake will not ruin the rest. A cold egg holds its yolk together more firmly than a room-temperature one, so it carries less risk of breaking.
Why is egg white so sensitive to fat?
As egg white is whipped, its proteins form a thin network around air bubbles; fat molecules get in the way of that network forming and stop the proteins from bonding to each other properly. Plastic bowls tend to hold an invisible film of fat on their surface, which makes glass or metal a more reliable choice than plastic for whipping whites. Wiping the bowl and whisk with a few drops of lemon juice or vinegar is a simple way to neutralise any trace of fat and make whipping easier.
What stages should you follow to reach stiff peaks?
The white should be foamed at low speed first, and the speed raised gradually once it starts gaining volume; whipping at high speed from the start leaves the bubbles uneven and fragile. If sugar is being added, it should go in gradually once the white starts foaming, not all at once; sugar added too early delays the white from reaching full volume. The white has reached stiff peaks once it holds a point standing straight up when the whisk is lifted; if the point flops straight over, it needs a few more minutes of whipping.
Can over-whipped white be saved?
Over-whipped white loses its smooth shine and turns clumpy and dull; a white in this state cannot be fully fixed, but adding one more raw white and whisking gently again can partly bring it back. Under-whipped white is still runny and will not hold a shape; the fix here is simple, just keep whisking patiently.