Emulsifier
An emulsifier is an additive which helps two liquids mix. For example, water and oil separate in a glass, but adding an emulsifier will help the liquids mix together. Some examples of emulsifiers are egg yolks and mustard. An emulsifier consists of a water-loving hydrophilic head and an oil-loving hydrophobic tail. The hydrophilic head is directed to the aqueous phase and the hydrophobic tail to the oil phase. The emulsifier positions itself at the oil/water or air/water interface and, by reducing the surface tension, has a stabilising effect on the emulsion.