Emulsifiers

Emulsifiers are substances that stabilize emulsions, mixtures of two immiscible liquids such as oil and water, by reducing interfacial tension and by forming a protective interfacial layer around droplets. Most emulsifiers are amphiphilic, containing both hydrophilic and lipophilic regions, which enables them to adsorb at the oil–water interface and lower the energy required to create and maintain dispersed droplets.

Emulsions stabilized by emulsifiers can be oil-in-water or water-in-oil, depending on the emulsifier’s hydrophilic-lipophilic balance (HLB). Higher HLB values favor oil-in-water systems, while lower values favor water-in-oil systems. In addition to molecular surfactants, solid particles can stabilize emulsions, creating Pickering emulsions that rely on steric hindrance and particle coverage to prevent coalescence.

Common food emulsifiers include lecithin (from soy or egg), mono- and diglycerides, polysorbates, sorbitan esters, and stearoyl lactylates. In cosmetics and pharmaceuticals, emulsifiers such as polysorbates, glyceryl stearates, and esters are widely used. Some natural emulsifiers are proteins (milk, egg, soy) that can unfold at interfaces to provide stabilization.

Regulatory agencies approve emulsifiers for foods, cosmetics, and medicines, often assigning codes in different regions (for example, in the European Union, lecithin is E322 and mono- and diglycerides are E471). Safety assessments consider allergenicity, dietary restrictions, and exposure levels. Emulsifiers improve texture, stability, and shelf life but can affect flavor or viscosity and may be costly or sensitive to processing conditions.