Also: emulsify, emulsion, emulsified sauce, emulsified
A stable mixture of two liquids that normally refuse to combine — typically oil and water — held together by an emulsifier that coats microscopic droplets of one and keeps them suspended in the other.
Why it works
Oil and water repel each other at the molecular level. Oil molecules are non-polar (water-fearing); water molecules are polar (water-loving). Left alone, they separate. Emulsification breaks this separation by two mechanisms at once: mechanical force (whisking, blending, shaking) that shatters the oil into microscopic droplets, and a chemical go-between that coats those droplets and keeps them from recombining. (McGee, On Food and Cooking, 2nd ed., pp. 628–631.)
The chemical go-between is the emulsifier. Egg yolk (rich in lecithin), mustard, honey, garlic paste, and miso all work because they have molecules with both hydrophilic and hydrophobic ends — one end grips the oil, the other faces the water, creating a stable bridge. Without an emulsifier, a violently shaken vinaigrette breaks apart within minutes. With one, mayonnaise holds for weeks.
Temperature matters. Cold ingredients produce smaller, more stable droplets than warm ones. Warmed butter emulsifies in hollandaise because heat keeps butterfat liquid, but the mixture sits on a knife's edge: too hot and the emulsion breaks; too cold and the butter solidifies. (Modernist Cuisine, vol. 4, pp. 178–185.)
How to use it
- Start with a tiny amount of oil. A cold egg yolk can emulsify a litre of oil — but only if you add it drop by drop at first, then thicken to a steady thin stream.
- Keep everything the same temperature. Cold mayonnaise from cold yolk and cold oil. Warm hollandaise from warm yolk and warm butter. Mixing temperatures splits the emulsion.
- Whisk steadily in one direction. The goal is sustained shear force breaking oil droplets into finer and finer pieces.
- If it breaks, don't panic. Start a fresh base — a new yolk, or a teaspoon of cold water with a dab of mustard — and whisk the broken mixture into it slowly.
Common mistakes
- Adding oil too fast at the start. The emulsifier needs to coat each new droplet before the next arrives.
- Skipping the acid in a vinaigrette. Oil and shallot alone will break within minutes; even a teaspoon of vinegar stabilises it.
- Overheating hollandaise. Above around 70°C the yolks begin to cook and the emulsion curdles into scrambled eggs.
See also
Examples
(auto-appended as the user logs cooks that touch this concept)
Sources
- McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed. Scribner, 2004. pp. 628–631.
- Myhrvold, Nathan et al. Modernist Cuisine: The Art and Science of Cooking, vol. 4. Cooking Lab, 2011. pp. 178–185.