Vol. X · Emulsions, Foams and Gels Plate 3 of 11vinaigrette, dressing, oil, vinegar, ratio, mustard, honey, temporary emulsion, separationMT

Vinaigrette.

Three parts oil to one of vinegar, a pinch of salt, a spoon of mustard and a good shake: the simplest emulsion in the kitchen, and the shortest-lived.

A vinaigrette is oil droplets in vinegar (or the reverse, if there is much more oil), made by shaking or whisking. The droplets are large — tens of micrometres — because a fork or a jar cannot break oil finely, and with no strong emulsifier they rise and merge within minutes (X.1). That is fine: a vinaigrette needs to hold only from the bowl to the plate, and a quick shake brings it back.

The classic ratio is three parts oil to one part acid, adjusted to the acid's strength and the salad: a mild rice vinegar takes less oil, a sharp sherry vinegar more. Salt and sugar dissolve in the vinegar, not the oil, so they go in first. Mustard, honey, miso, a little crushed garlic or a spoonful of yoghurt thicken the water phase and coat the droplets, slowing separation many-fold. The workshop shakes a jar.

Below: minutes for a 3 cm jar of dressing to separate against droplet size, plain and with a thickened vinegar phase (Stokes's law with the Krieger–Dougherty thickening of a crowded mixture; the thickener's effect is a teaching value).

What you will learn
Workshop
Separation time: 3 cm divided by the Stokes rising speed of an oil droplet in the vinegar phase, whose viscosity is raised by the crowding of droplets (Krieger–Dougherty) and, with mustard or honey, about fivefold (teaching value).

Shake, dress, serve

A plain vinaigrette shaken to droplets of about 50 µm separates across a 3 cm jar in about 17.4 minutes in this model; with a spoon of mustard or honey thickening the vinegar, about 87 minutes; blended to 15 µm with mustard, about 16 h 7 min — a dressing that holds through a meal. Blending finer still, with an egg yolk, gives a creamy dressing that does not separate at all: by then it is a thin mayonnaise (X.4).

Method: dissolve salt (and any sugar) in the vinegar, add mustard or other thickener, then whisk or shake in the oil. Taste on a leaf, not a spoon, because oil coats the tongue differently on a salad. Dress just before serving and toss gently: salt and acid draw water from leaves and wilt them within minutes (III.8), which is also why Chinese 凉拌 dishes are dressed at the table or with sturdier vegetables such as cucumber and wood-ear.

At the stove

Make a 3:1 vinaigrette in a jar, shake it and time the separation. Add half a teaspoon of mustard, shake again and time it. Then blend a little with a stick blender and watch it stay creamy.

The French word vinaigrette, "little vinegar", appeared in cookery books in the seventeenth century; earlier, Roman cooks dressed lettuce with oil, vinegar and the fish sauce garum.

Terms

Vinaigrette
A dressing of oil and acid made into a temporary emulsion.
Temporary emulsion
One that separates in minutes without a strong emulsifier.
Water phase
The vinegar and everything dissolved in it.
凉拌
Chinese cold-dressed dishes.
A vinaigrette is a temporary emulsion; smaller droplets and a thicker vinegar slow its separation. Salt goes into the vinegar.

Sources

  1. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.
  2. H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.