Emulsifiers for the Food Industry

Abstract

Surfactant is a coined word (from surface active agent) that is applied to molecules that migrate to interfaces between two physical phases and thus are more concentrated in the interfacial region than in the bulk solution phase. The key molecular characteristic of a surfactant is that it is amphiphilic in nature, with the lipophilic (or hydrophobic) part of the molecule preferring to be in a lipid (nonpolar) environment and the hydrophilic part preferring to be in an aqueous (polar) environment. If a surfactant is dissolved in one phase of an ordinary mixture of oil and water, some portion of the surfactant will concentrate at the oil–water interface, and at equilibrium the free energy of the interface (called interfacial or surface tension, γ) will be lower than in the absence of the surfactant. Putting mechanical energy into the system (e.g., by mixing) in a way that subdivides one phase will increase the total amount of interfacial area and energy; the lower the amount of interfacial free energy per unit area, the larger the amount of new interfacial area that can be created for a given amount of energy input. The subdivided phase is called the discontinuous phase, and the other phase is the continuous phase. Examples of surfactants are monoglyceride (nonionic), stearoyl lactylate (anionic), and lecithin (amphoteric). Keywords: surfactants; emulsifier; emulsion; surface active agent; interface; foams; energetics; monoglycerides; lecithin; stearoyl lactylate