Emulsifier is any of numerous food chemical additives that support the suspension of one liquid in another that normally separate when they are mixed, for example as in the mixture of oil and water in margarine, shortening, ice cream, and salad dressing.
The basic structure of an emulsifying agent comprises 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 stabilizing effect on the emulsion.
The extent to which the hydrophilic or lipophilic character dominates is represented by the HLB value of the surfactant (HLB = Hydrophilic-Lipophilic Balance). A high HLB value (10 to 18) indicates a hydrophilic substance suitable for emulsifying fats or oils in water. Substances with a low HLB (3 to 8) are lipophilic and suitable for water-in-oil emulsions.
Emulsifiers are closely related to stabilizers, which are substances that maintain the emulsified state. The consistency of food products may also be improved by the addition of thickeners, used to add body to sauces and other liquids, and texturizers.