Vegan mayonnaise: how egg-free emulsions hold oil
Mayonnaise is an emulsion: tiny droplets of oil suspended in a water-based liquid. Normally egg yolk does the holding. Without it, three plant-based routes work at home: aquafaba (the liquid from cooked chickpeas), unsweetened soy milk, and a cooked starch paste. Each holds the oil in a different way, and each has its own way of failing. Understanding the mechanism makes the difference between a thick, glossy sauce and a greasy puddle, and it also explains how to rescue one that has split. The same ideas apply to aioli, tartare sauce, dressings and dips.
What an emulsion needs
Oil and water do not mix. To get a smooth sauce you must break the oil into very small droplets and then stop them joining back together. Two things achieve that.
- Energy: whisking, or a stick blender or food processor, breaks the oil into droplets. Adding the oil slowly gives the blades time to keep the droplets small.
- A stabiliser: something in the water phase that coats the droplets or thickens the liquid around them so they cannot merge. In egg mayonnaise that is lecithin and protein from the yolk. In vegan versions it is protein, starch, or both.
Mustard and a little acid (lemon juice or vinegar) help flavour and stability, and salt seasons. Acid also thickens some proteins, which is useful with soy milk.
The three routes compared
| Base | How it holds the oil | Typical method | Texture | Watch for |
|---|---|---|---|---|
| Aquafaba | Proteins and dissolved carbohydrates from the chickpeas coat the droplets and thicken the water | Blend or whisk aquafaba with mustard and acid, then add oil in a thin stream | Glossy, close to egg mayonnaise | Thin or very dilute aquafaba gives a loose sauce; reduce it first if it seems watery |
| Unsweetened soy milk | Soy protein and natural lecithin coat the droplets, and acid thickens the protein | Stick blender in a tall jar: soy milk and oil blended without moving until it thickens, acid added at the end | Thick and creamy | Use plain unsweetened soy milk; sweetened or flavoured versions behave differently |
| Cooked starch paste | Starch swells in water and holds the droplets in place physically | Cook cornflour (cornstarch) with water to a paste, cool, then blend in oil and seasonings | Light, set, a little jelly-like | Can taste starchy if undercooked |
Silken tofu blended with oil, acid and mustard is a fourth route that works on the same protein principle as soy milk and gives a thicker, spoonable result.
Amounts as starting points
Published recipes differ, and aquafaba from different cans varies in strength, so these are starting points rather than exact formulas. For aquafaba mayonnaise, around 3 tablespoons (45 ml) of aquafaba is commonly used with about three quarters of a cup to 1 cup (180 to 240 ml) of oil. For soy milk mayonnaise, about a quarter cup (60 ml) of soy milk is commonly used with roughly three quarters of a cup to 1 cup (180 to 240 ml) of oil, with a tablespoon of lemon juice or vinegar added at the end. Add seasoning to taste, and stop adding oil when the sauce is as thick as you like.
A neutral oil gives the cleanest flavour. Extra virgin olive oil can taste bitter when blended at high speed, so many cooks use a neutral oil for most of the volume and stir in a little olive oil at the end. Refined coconut oil sets firm when chilled and gives a stiffer result.
Method tips for each base
- Use a narrow jar or jug that just fits the stick blender head. A wide bowl spreads the ingredients thin and the blender cannot catch them.
- Have the ingredients at a similar, moderate room temperature rather than straight from the fridge.
- Start the oil slowly, a few drops at a time, until the mixture turns pale and thick. Then it can go in a thin stream.
- With the soy method, put the blender head at the bottom and keep it there until you see white emulsion climbing the jar, then lift slowly.
- Stop blending once the sauce is thick.
- Add the acid at the point the recipe says: with aquafaba it goes in at the start with the mustard, and with soy milk it can go in at the end to thicken.
Why it splits, and how to rescue it
| Symptom | Likely cause | Fix |
|---|---|---|
| Oil pools on top, sauce looks curdled | Oil added too fast, so droplets joined up | Put 1 tablespoon (15 ml) of aquafaba or soy milk in a clean bowl, then whisk the broken sauce into it a spoonful at a time. |
| Thin and runny but not separated | Too little oil for the liquid, or very watery aquafaba | Keep blending in oil slowly. A tiny pinch of xanthan gum can also thicken a loose sauce. |
| Bitter taste | Extra virgin olive oil blended at high speed | Use neutral oil for most of the volume and fold olive oil in by hand. |
| Splits in the fridge | Emulsions can loosen slowly in storage | Whisk it back together, or use the rescue above. |
| Splits after freezing | Freezing breaks emulsions | Do not freeze mayonnaise; make smaller batches. |
| Starchy or pasty flavour | Starch not cooked through | Cook the paste for a little longer, and cool it fully before adding oil. |
The rescue works because a small amount of fresh stabiliser can take on the oil gradually, so the key is slowness: add the broken sauce a spoonful at a time and whisk each addition in before the next.
Storing it safely
Homemade vegan mayonnaise has no cooked or preserved shelf life like a jar from a shop. Keep it in a clean jar in the fridge, use clean spoons, and use it within a few days. Throw it away if it smells or looks off. If in doubt, throw it out. Garlic or herbs kept in oil are a recognised food-safety concern (botulism risk) whenever they sit at room temperature, so keep garlic aioli chilled at all times, use it within a few days, and never leave it out.
Allergy and gluten notes
These sauces are free of egg, but soy milk, tofu, chickpea liquid and mustard are each allergens or common sensitivities for some people, so choose the base accordingly. Vinegar and mustard labels vary: malt vinegar is made from barley, and some mustards use other ingredients, so check labels for gluten. For coeliac disease or any allergy, rely on the label and talk to your doctor or dietitian.
What this guide is based on
- That an emulsion needs energy plus a stabiliser, that egg yolk lecithin is the usual stabiliser, and that protein, starch and mustard can play that role in vegan versions, is general cooking and food-science knowledge.
- The amounts (around 3 tablespoons of aquafaba with three quarters to 1 cup of oil, and about a quarter cup of soy milk with three quarters to 1 cup of oil) are commonly published starting points that vary between recipes. They are not from our own testing.
- The storage advice (fridge, a few days, discard if in doubt) is conservative general guidance rather than a tested shelf life. That freezing breaks an emulsion, and that extra virgin olive oil can turn bitter when blended hard, are widely reported cooking observations.
- Remarks on allergens, gluten, vinegar and mustard are general. Labels differ by country, so check them and ask a doctor or dietitian about your own needs.