Emulsioonides

Emulsions are heterogeneous colloidal systems in which droplets of one liquid (the dispersed or internal phase) are dispersed within another immiscible liquid (the continuous phase). The droplets can range from submicron to several micrometers in size. Emulsions are typically metastable and will eventually separate without stabilization.

There are several principal types. Oil-in-water (O/W) emulsions contain oil droplets dispersed in water and are common in foods, cosmetics, and some pharmaceuticals. Water-in-oil (W/O) emulsions have water droplets in a continuous oil phase and are used in specialized applications such as certain creams and lubricants. Multiphase or multiple emulsions, such as water-in-oil-in-water (W/O/W) or oil-in-water-in-oil (O/W/O), contain droplets within droplets and are used in advanced delivery systems.

Stabilization is achieved with emulsifiers or stabilizers that reduce the interfacial tension between the two liquids and create a protective layer around droplets. Surfactants are the most common stabilizers; solid particles can also stabilize emulsions in Pickering systems. The method of preparation, including high-energy processes like homogenization or ultrasonication and low-energy approaches such as phase inversion, influences droplet size and stability.

Stability challenges include creaming or sedimentation due to density differences, coalescence where droplets merge, flocculation where droplets aggregate, and Ostwald ripening where droplets dissolve and re-form at larger sizes. Rheology and droplet size distribution are key properties that determine texture, mouthfeel, and flow behavior.

Applications span food, cosmetics, pharmaceuticals, and industrial sectors. Emulsions enable controlled delivery of flavors, nutrients, and active ingredients, as well as products like lotions, creams, and lubricants.