Who says oil and water don’t mix? Take a look at emulsion (ih-MUHL-shuhn), and you will see that they do. An emulsion is a mixture of incompatible fluids in which tiny droplets of one liquid are suspended in the other. Everyday kitchen emulsions include vinaigrettes, mayonnaise and hollandaise sauce. For the cook, getting incompatible liquids to bond requires serious mixing.
When you produce an emulsion, you’ve created something mind-boggling––a single tablespoon of oil added to a mayonnaise breaks into about 30 billion individual droplets. But the procedure isn’t difficult. To make mayonnaise, you simply mix eggs with lemon or vinegar, then whisk vigorously while slowing adding oil. A vinaigrette can be created by shaking. Since the ingredients’ natural behavior is to repel each other, a vinaigrette that’s been sitting around for a while will need to be re-shaken.
To produce more stable emulsions, you need an emulsifier. Eggs contain a natural emulsifier called lecithin. The casein proteins in milk and cream can also do the job. From there, the list of common emulsifiers veers into items familiar only to those with an advanced degree in Chemistry. Emulsifiers are found in everything from commercial ice cream to the sauce on your Big Mac and include such items as diglycerides, polysorbates, sorbitan monostearate and xanthan gum.
—By Jo Marshall, a food writer in Deephaven, Minn.