Emulsifiers: Types and Uses

Emulsions are composed of two immiscible liquids where one is dispersed as individual droplets within the other. Typical food emulsions are oil-in-water and water-in-oil. Most emulsions are not stable for long periods of time and will quickly separate into the two separate components. Emulsifiers are surface-active agents that act at the interface between the two immiscible liquids. Their main roles are to promote emulsion formation and to stabilize the emulsion. Emulsifier molecules contain an oil-soluble, lipophilic tail that reacts with the oil and a water-soluble, hydrophilic head that reacts with the water at the interface of the dispersed droplet. These interactions decrease the surface tension of the droplet and allow it to be to be subdivided into smaller droplets during mixing, thus assisting in creating a more stable emulsion. Emulsifiers maintain the stability of the emulsions by forming barriers around the dispersed droplets, which prevent them from coalescing. The mechanism of barrier formation is determined by the properties of the emulsifier and includes electrostatic repulsion, creation of a 'bound' water layer, and steric hindrance. There are many types of emulsifiers with different functionalities that are used in a wide variety of food products.