An emulsifier is a chemical that encourages the suspension of one liquid in another so that they form one homogenous substance. They are often used as food additives.
As food additives, emulsifiers include algin and carageenan, which are algae products, and soy lecithin. Eggs and mustard are natural emulsifiers as well.
Emulsifiers are used to make noncompatible components of food, such as oil and water, blend smoothly rather than remain separate. They also help to keep food fresh longer. Emulsifiers are used in baking, candy-making, salad dressings, frozen desserts and coffee whitener, among other products.
Oil is hydrophobic, meaning that it does not dissolve in water. Water and certain other molecules that do not dissolve in oil are called is hydrophilic, meaning they have an affinity for water. Emulsifiers are molecules with a hydrophobic end and a hydrophilic end, allowing the two incompatible molecules to become compatible.