Emulsifier
An emulsifier is a substance that helps two liquids that don't mix, usually oil and water, stay blended in an emulsion. Each emulsifier molecule has one end attracted to water and one end attracted to fat, so it sits on the surface of droplets and keeps them from merging.
How it works
Picture a tadpole. The head is hydrophilic (water-loving) and the tail is lipophilic (fat-loving). When you whisk oil into a water-based liquid, emulsifier molecules rush to the boundary of each oil droplet, tails in the oil and heads in the water.
That coating does two jobs:
- It lowers the tension between oil and water, so droplets form more easily and smaller.
- It acts like a bumper, stopping droplets from touching and fusing back together.
Kitchen emulsifiers
| Emulsifier | Active part | Used in |
|---|---|---|
| Egg yolk | Lecithin and lipoproteins | Mayonnaise, hollandaise, aioli |
| Mustard | Mucilage and proteins | Vinaigrette, mayo |
| Honey | Thickness plus trace proteins | Dressings |
| Garlic paste | Fibre and small particles | Aioli, toum |
| Milk and cream | Casein and whey proteins | Pan sauces, ice cream |
| Aquafaba | Proteins and saponins | Vegan mayo |
One large egg yolk (about 18 g) can emulsify well over 250 ml (1 cup) of oil, provided you add the oil slowly.
Stabilizers vs emulsifiers
Emulsifiers coat droplets. Stabilizers like xanthan gum, starch or gelatin thicken the continuous phase so droplets can't drift and collide. Many sauces use both: mustard in vinaigrette both coats droplets and thickens.
Industrial emulsifiers
On labels you'll see soy or sunflower lecithin, mono- and diglycerides, and polysorbates. They keep chocolate fluid, bread soft and salad dressings uniform on the shelf.
Tips for using emulsifiers
- Add the emulsifier to the water phase first, then whisk in the fat.
- Use roughly 1 tsp (5 g) mustard per 120 ml (½ cup) vinaigrette.
- Keep egg-based sauces below about 70 °C / 160 °F or the yolk proteins set and the sauce scrambles.
Questions
What are common emulsifiers in the kitchen?
Egg yolk, mustard, honey, garlic paste, miso, tomato paste and milk proteins all help hold oil and water together. Egg yolk is the most powerful because of its lecithin.
Is mustard an emulsifier?
Yes. Mustard seed coating contains mucilage and proteins that coat oil droplets and thicken the water phase, which is why a spoonful keeps vinaigrette from separating so quickly.
Are emulsifiers in food bad for you?
Kitchen emulsifiers such as yolk and mustard are ordinary foods. Industrial emulsifiers like soy lecithin and mono- and diglycerides are approved for use in Canada and the US at food levels.
Can you make mayonnaise without an emulsifier?
Not a stable one. Without an emulsifier the oil droplets merge and separate. Egg-free versions rely on other emulsifiers such as aquafaba, soy milk protein or mustard.