Emulsifiers are the ingredients in a solution that mix together substances that normally would not mix, i.e. oil and water. The resulting solution is an emulsion. Emulsifiers are used in food, hygiene/cosmetics products, medicine, and a variety of other products and applications.
      How They Work
Most emulsions deal with water and oil, which normally separate into two layers when you add them together. There are two basic types of emulsion: water-in-oil and oil-in-water; the first deals with oil droplets dispersed in water, and the second, vice-versa. Emulsifier molecules have one hydrophilic (water-loving) end and one lipophilic (fat or oil-loving) end. In an oil-in-water emulsion, the lipophilic ends of the molecules surround the oil droplets, with their hydrophilic ends exposed to the surrounding water. In this way, the oil droplets may move around in a shield of emulsifiers, allowing them to disperse freely throughout the solution. Water-in-oil emulsions work the same, with the orientation of the emulsifier molecules reversed to accommodate the water droplets.
      Hygeine/Cosmetics
Various cosmetics creams, such as moisturizers, contain emulsifiers. Lighter, less greasy feeling creams are oil-in-water emulsions; heavier creams used to treat rough skin are water-in-oil emulsions, with oil as the main ingredient. Liquid soaps, toothpastes and other body care products also contain emulsifiers. Emulsifiers have the ability to optimize the concentration of certain nutrients in an emulsion. For example, in hair conditioners, some conditioning agents can damage hair if not properly diluted in the solution.
      Food
The food industry uses many emulsifiers, both natural and synthetic, for a number of reasons. Common natural emulsifiers are egg, soybean oil, palm oil, rapeseed oil and sunflower oil. Other emulsifiers are synthesized to better match the qualities and ingredients of a given product. Emulsifiers are used in dairy products such as cream cheese and ice cream in order to enhance and differentiate textures. In candy products they are used to improve crystallization and to create popular chewy or gooey textures. In addition, they are used to improve the shelf-life of many products, such as as jarred peanut-butter and sauces as well as breads.
      Other Uses
Other common industries that use emulsions are agriculture, pharmaceuticals and paints/inks. In agriculture, they are used to regulate the concentration of fertilizers and pesticides, improving dilutability and spray-ability of solutions with powerful biocides that may be damaging if not properly dispersed. In pharmaceuticals, emulsifiers are incorporated into drugs in order to regulate dosages and to make medicines more palatable. In paints and inks, they are used to keep colors homogeneous, to help them dry more quickly, and to provide waterproof coats without affecting pigment.
      Negative Effects
Some emulsifiers have been found to contain harmful chemicals, especially in the highly synthetic chemical make-ups of many cosmetic products. For example, polyethylene glycol (PEG) compounds have been found to contain traces of carcinogens. Certain types of emulsifiers called surfactants, also used in body-care products, have caused allergic reactions as well as skin and eye problems.