Emulsifying

Emulsifying is the process of creating or stabilizing an emulsion, a mixture in which droplets of one immiscible liquid are dispersed in another. Emulsification relies on emulsifiers, substances that adsorb at the interface between the immiscible liquids, reduce interfacial tension, and form a protective film around droplets to slow coalescence.

Common emulsifiers include amphiphilic molecules such as proteins (egg white and casein), phospholipids (lecithin), and various surfactants (polysorbates and sorbitan esters). Solid particles can also stabilize emulsions in Pickering-type systems. In foods, emulsifiers enable products like milk, salad dressings, and mayonnaise; in cosmetics, they stabilize creams and lotions; in pharmaceuticals, they aid delivery of oil-soluble actives.

Emulsions are typically oil-in-water or water-in-oil, with many products employing oil-in-water systems. More complex, multiple emulsions such as water-in-oil-in-water are used in specialty formulations. Droplet size, distribution, and the properties of the interfacial film influence appearance, texture, and stability.

Stability is affected by creaming or sedimentation, coalescence, Ostwald ripening, and flocculation. Stabilization depends on effective interfacial coverage, interfacial rheology, and the viscosity of the continuous phase, as well as electrostatic or steric repulsion around droplets.

Emulsification methods range from high-shear mixing and homogenization to ultrasonic processing and phase inversion techniques. The choice depends on formulation, desired droplet size, and processing constraints.