emulsification

Emulsification is the process of forming and stabilizing an emulsion, a system in which droplets of one immiscible liquid are dispersed within another. Most emulsions are thermodynamically unstable and tend to separate over time, but can be stabilized by emulsifiers that lower interfacial tension and form a protective film around droplets. Emulsification typically requires energy input to overcome interfacial tension and to generate small droplets.

Emulsions come in several types. The most common are oil-in-water (O/W), where oil droplets are dispersed in water, and water-in-oil (W/O), where water droplets are dispersed in oil. Complex or multiple emulsions such as O/W/O and W/O/W also exist. The choice depends on the intended use and the properties of the phases. Emulsifiers include surface-active agents such as soaps and food-grade surfactants, proteins, phospholipids, and solid particles (in Pickering emulsions). They work by adsorbing at the oil–water interface to reduce interfacial tension and provide electrostatic or steric stabilization. Hydrophilic–lipophilic balance (HLB) values help guide compatibility between emulsifier and phases.

Formation methods involve energy input through high-shear mixing, homogenization, rotor-stator devices, ultrasonic processing, or membrane emulsification. Droplet sizes range from nanometers to several micrometers; smaller droplets generally improve stability but require more energy. Stability can be compromised by creaming, sedimentation, coalescence, flocculation, or Ostwald ripening, and is influenced by temperature, pH, ionic strength, and the relative volumes of the phases.

Applications span food products, cosmetics, pharmaceuticals, agriculture, and industrial formulations, where controlled texture, appearance, and delivery are essential.