By Harold McGee
The most commonly and easily made emulsified sauce is the simple oil-and-vinegar salad dressing known as vinaigrette, from the French word for “vinegar.” Vinaigrette does a good job of clinging to lettuce leaves and other vegetables, and lending a refreshing tart counterpoint to their taste. The standard proportions for a vinaigrette are 3 parts oil to 1 vinegar, similar to the proportions in mayonnaise, but the preparation is much simpler. The liquids and other flavorings— salt, pepper, herbs—are often simply shaken into a cloudy, temporary emulsion at the last minute, then poured onto and mixed with the salad. When made in this casual way, a vinaigrette is the odd sauce out: instead of being oil droplets dispersed in water, it’s water (vinegar) droplets dispersed in oil. Without the help of an emulsifier, one part of water simply cannot accommodate three parts of oil, so the more voluminous phase, the oil, becomes the continuous phase.