Origin debated — likely Mahon, Menorca (captured by French forces in 1756) or southern French Languedoc tradition; adopted into French haute cuisine and spread globally through the 19th century
Mayonnaise is a stable oil-in-water emulsion in which fine droplets of oil are dispersed within a water phase composed of egg yolk, acid (lemon juice or vinegar), mustard, and salt. The emulsification is stabilised by lecithin and proteins in the egg yolk, which migrate to the oil-water interface and prevent coalescence of the oil droplets. Understanding the science enables consistent production and diagnosis of emulsion failures. Egg yolk contains approximately 30% dry weight as lecithin (primarily phosphatidylcholine) — the principal emulsifier. When egg yolk is beaten with acid and salt and oil is added slowly, the mechanical energy of beating breaks oil into increasingly fine droplets while the yolk emulsifiers coat each droplet's surface, preventing re-coalescence. The maximum oil-to-yolk ratio is approximately 200–250ml oil per large egg yolk — exceeding this exhausts the available emulsifier and the emulsion breaks. Acid serves two roles: flavouring and emulsion stability. Acidic pH causes egg yolk proteins to unfold partially, exposing more hydrophobic regions that preferentially migrate to the oil-water interface and improve emulsification effectiveness. Mustard contributes mucilage (a complex polysaccharide) that acts as an additional emulsifier and thickener, as well as flavour. The hand method — whisking by hand rather than using a blender — demonstrates emulsion science most clearly. Oil must be added in an extremely thin, slow stream at the beginning when the ratio of oil to emulsifier is high — even a small excess of oil at this critical stage can break the emulsion. Once the emulsion begins to thicken and stabilise (typically after the first 30–50ml of oil is incorporated), oil can be added in a thin stream with less precision. A room-temperature egg yolk and room-temperature oil emulsify more readily than cold ingredients. Broken mayonnaise can be rescued: start with a clean bowl, a fresh egg yolk, a small amount of acid, and slowly whisk the broken mixture into the new yolk — the emulsifier in the new yolk absorbs and stabilises the broken droplets.
Neutral and rich with bright acid balance — flavour character is determined entirely by the quality of the oil, acid, and aromatics; emulsion stability determines texture quality
Add oil drop by drop at the beginning — the critical period when oil-to-emulsifier ratio is highest and emulsion is most fragile Maximum oil per egg yolk is approximately 200–250ml — exceeding this breaks the emulsion regardless of technique Room temperature ingredients emulsify more readily than cold — remove egg yolk from fridge 30 minutes before use Mustard provides additional emulsification and is important for emulsion stability, not just flavour Acid (vinegar or lemon juice) unfolds yolk proteins to expose emulsifying surfaces — always add acid before the oil Broken mayonnaise is rescued by whisking slowly into a fresh yolk — the new yolk's emulsifiers absorb and stabilise the broken mixture
For foolproof blender mayonnaise, use an immersion blender with the egg yolk and acid in the bottom of a narrow jar — pour all the oil on top and plunge the blender, then raise slowly as it emulsifies For aioli (Provençal garlic mayonnaise), begin with roasted garlic paste in the bowl before the yolk — the roasted garlic provides additional emulsification surface For stable mayonnaise that holds on buffets or in warm environments, add 0.3% xanthan gum to the water phase — it dramatically increases viscosity and prevents weeping A clean resting bowl, no oil residue, and a room-temperature yolk are the three most important preparation steps for a beginner learning hand mayonnaise For a lighter result, replace 30% of the oil with a light flavoured broth or cold reduction — the result is a semi-emulsion with dramatically reduced fat content
Adding oil too fast at the beginning, before sufficient emulsifier is present to coat the droplets — this is the most common cause of breaking Using cold oil directly from the refrigerator — cold oil is more viscous and breaks into larger, harder-to-emulsify droplets under mixing Exceeding the emulsifier capacity of the yolk by adding too much oil, resulting in a grainy, broken mass that cannot be incorporated Not adding all the acid at the beginning — adding vinegar or lemon juice at the end after the emulsion has formed can cause it to break Using light olive oil expecting a neutral result — even light olive oil has enough phenolic bitterness to produce unpleasant flavour