MAYONNAISE

MAYONNAISE IS A THICK, CREAMY emulsion of egg yolk and oil with a little acid and some seasonings. An emulsion is a mixture of two things that don't ordinarily mix, such as oil and water or oil and vinegar. The only way to mix them is to stir or whisk so strenuously that the two ingredients break down into tiny droplets. Many of the like droplets will continue to find each other and recoalesce into pure fluid. Eventually, however, one of the fluids will disintegrate entirely into droplets so tiny that they remain separated by the other fluid, at least temporarily.

The liquid that goes into this droplet form is referred to as the dispersed phase of an emulsion because the droplets are dispersed throughout. The liquid that surrounds the droplets is called the continuous phase. Because the continuous phase forms the surface of the emulsion, that's what the mouth and tongue feel and taste first. In mayonnaise, the egg yolk and lemon juice are the continuous phase (that's why something that is 95 percent oil doesn't taste greasy), and the oil is the dispersed phase.

Mayonnaise works because egg yolk is such a good emulsifier and stabilizer. But sometimes mayonnaise can "break," as the ingredients revert back to their original liquid form. To keep mayonnaise from breaking, we found it first necessary to whisk the egg yolk and lemon juice thoroughly (the egg yolk itself contains liquid and fat that must be emulsified). It is equally important to add the oil slowly to the egg yolk. Remember, just a couple of tablespoons of yolk and lemon juice must be "stretched" around ³/₄ cup of oil.

We like the flavor of corn oil in our basic mayonnaise. It produces a dressing that is rich and eggy with good body. Canola oil makes a slightly lighter, more lemony mayo. Extra-virgin olive oil is too heavy and assertive in mayonnaise, unless garlic is added to make a Mediterranean-style mayonnaise, such as aïoli.