Why will my mayonnaise not thicken?
A mayonnaise that stays liquid has not split — it has never emulsified. The four causes, how to tell which one applies, and how to get it thick from where you are.
- Difficulty
- intermediate
- Time
- 10 min
- Read
- 4 min
Short answer
If it is thin but uniform, the emulsion has not formed: the oil went in too fast at the start, or the ingredients were at different temperatures. Stop adding oil, whisk hard for a minute, and if nothing happens start a fresh yolk in a clean bowl and add the thin mixture to it drop by drop.
There are two different failures and people call both of them splitting. A split mayonnaise has visibly separated into oil sitting on a thin yellow liquid. A mayonnaise that will not thicken is uniform, looks like thin cream, and never gets any further. That second one is an emulsion that never started, and it is the more common of the two.
Step by step
- Look at it and decide which failure you have.Uniform and thin, pale, no visible oil layer: never emulsified. Curdled-looking with free oil on top or around the edge: split. The rescues differ slightly, so tell them apart first.
- Stop adding oil immediately.Every further millilitre makes the rescue harder because it increases the oil the emulsifier has to cover. Put the jug down.
- Check the temperature.If the bowl feels cold, stand it in a bowl of hand-hot water for a minute and whisk again. A cold yolk cannot spread across the oil surface properly and a surprising number of thin mayonnaises simply come together once warmed.
- Whisk hard for a full minute before doing anything else.Sometimes there is simply not enough mechanical work in it yet. Sixty seconds of proper whisking with the bowl steadied is worth trying before you break another egg.
- If it is still thin, start again in a clean bowl with a fresh yolk.Whisk a fresh room-temperature yolk with a teaspoon of Dijon. Add one teaspoon of the thin mixture and whisk until it is thick. Do not add more until it is. Then add the thin mixture a tablespoon at a time, whisking each in fully.
- Finish and correct the seasoning.You have added an unseasoned yolk, so it will need salt and probably more acid. Loosen with a teaspoon of warm water if it has come out stiffer than you want.
Tips
- One yolk will hold about 200ml of oil. If you are past that and it is thinning, it is not a technique problem — you have run out of emulsifier.
- A teaspoon of Dijon mustard in the base makes a mayonnaise substantially harder to fail. It is genuine insurance, not seasoning.
- If you have no second egg, a teaspoon of mustard alone in a clean bowl will act as the starter for the rebuild. It works, and the result tastes more of mustard.
- Mayonnaise thickens slightly in the fridge. A sauce that is just short of where you want it will often be right after an hour chilled.
If it doesn't work
Thin and uniform, oil going in slowly, nothing happening
Cause: Too much oil went in before the emulsion had formed, so the droplets are too large and too few to crowd each other — Fix: Stop. Rebuild on a fresh yolk in a clean bowl, adding the thin mixture a teaspoon at a time until it thickens, then a tablespoon at a time.
Bowl and ingredients are cold to the touch
Cause: A cold yolk is viscous and does not spread over the oil droplets; cold oil is also harder to break up — Fix: Stand the bowl in hand-hot water for a minute and whisk again. Often that alone is enough.
It thickened, then loosened again as more oil went in
Cause: The oil has exceeded what one yolk can coat — usually somewhere past 200ml — Fix: Whisk a second yolk in a clean bowl and add the loose mayonnaise to it gradually. That raises the ceiling to about 400ml.
Thin and slightly grainy, made in a food processor
Cause: Too little mixture in the bowl for the blade to reach, so most of the oil is never sheared — Fix: Scale up to at least two eggs, or switch to a narrow jug and a stick blender, which reaches right to the bottom.
Questions people ask
Can I fix it by adding cornflour or more mustard?
No. Starch will thicken the watery part but it does nothing to the oil, and you get a thick, greasy paste that separates later. Mustard helps only as the base of a proper rebuild in a clean bowl, not stirred into the failed batch.
Does the type of oil matter?
Not for whether it emulsifies, but very much for taste. Extra virgin olive oil turns bitter when it is whisked hard, so a mayonnaise made entirely from it is often unpleasant. Use a neutral oil, or blend a quarter olive oil into three-quarters neutral.