An emulsifier (also known as an emulgent or surfactant) is a substance which stabilizes an emulsion. Examples of food emulsifiers are egg yolk (where the main emulsifying chemical is the phospholipid lecithin), and mustard, where a variety of chemicals in the mucilage surrounding the seed hull act as emulsifiers; proteins and low-molecular weight emulsifiers are common as well. In some cases, particles can stabilize emulsions as well through a mechanism called Pickering stabilization.
Emulsification
Both mayonnaise and hollandaise sauce are oil-in-water emulsions stabilized with egg yolk lecithin. Examples of emulsions include butter and margarine, espresso, mayonnaise
