Ever wonder why your homemade mayo turns from glossy and thick into a greasy yellow puddle halfway through? It didn't do anything wrong. You did — and that's the good news, because it's fixable.
What an emulsion actually is
Oil and water don't want to mix. Left alone, they separate immediately. An emulsion is a temporary peace treaty between them, brokered by a molecule called an emulsifier — in mayo, that's lecithin from egg yolk. Lecithin has one end that loves water and one end that loves fat. It lines up at the boundary between every tiny oil droplet and the water phase, holding them apart.
The result: thousands of oil droplets suspended in an aqueous base, thick and stable. As long as those droplets stay small and coated, you have mayo.
Why it breaks
Two things collapse an emulsion:
- You added oil too fast. The emulsifier hasn't had time to coat each droplet before the next wave of oil arrives. The droplets merge — and suddenly you have separate oil and liquid again.
- Temperature shock. Cold eggs straight from the fridge meeting warm oil creates uneven viscosity that the emulsifier can't bridge.
The rescue
The fix works because of the same science in reverse: you just need to rebuild the droplet structure from scratch.
Broken mayo or aioli:
- Crack a fresh egg yolk into a clean bowl.
- Add a small pinch of salt and a drop of mustard (extra emulsifier — not essential, but helpful).
- Whisk the broken mixture into the new yolk, a few drops at a time at first.
- Once it starts to thicken, you can pour slightly faster.
The new yolk supplies fresh lecithin. The broken sauce becomes the "oil" in your rebuilt emulsion.
Broken hollandaise:
Same logic, but heat is also in play. Pull the pan off heat. Whisk in a tablespoon of cold water and a fresh egg yolk, then return to very low heat — whisking continuously. You're re-emulsifying while keeping the temperature below 70°C, where egg proteins start to scramble.
Broken vinaigrette:
Vinaigrette is a temporary emulsion (no egg, less emulsifier), so re-shaking it is usually enough. For something more stable, add a small blob of mustard before shaking — mustard contains mucilage, which acts as a mild emulsifier and keeps things together longer.
Stop it happening next time
- Bring eggs to room temperature before you start.
- Add oil as a thin, steady drizzle — not a pour.
- If using a stick blender, start on low speed.
A broken emulsion isn't a disaster. It's just physics asking you to slow down.
