Mayonnaise

Whether you buy it in a jar or make it yourself at home, mayonnaise is an emulsion created by adding oil to egg yolks or whole eggs along with flavorings and seasonings.

The procedure for making mayonnaise involves slowly drizzling vegetable oil into the egg yolks and whisking until it thickens. Add the oil too fast and the emulsion will break, which means the oil and egg yolks separate. When done properly, a single egg yolk can absorb up to eight oz of oil. Typically we add some vinegar to the egg yolks. Besides contributing flavor, the acid in the vinegar also helps increase the amount of oil that the egg yolks can hold.

Incidentally, mayonnaise made with olive oil instead of vegetable oil is called aioli.

One word of caution is in order. Because the eggs aren't cooked, it's always a good idea to use pasteurized eggs when making your own mayonnaise.