Surface Active Agent
When a water droplet is in the air, surface tension, a force to reduce the surface area acts on the surface of the water, resulting in a spherical water droplet. Water and oil never mix together and separate into two layers even after the stirring.
When two immiscible substances are in contact, the contact surface is called interface. Interfacial tension, a type of surface tension, acts on the interface to separate the two substances from each other.
As interfacial tension increases, the force to separate two substances becomes stronger.
Surfactant reduces the interfacial tension and changes the properties of an interface.
Phenomena which seems impossible to happen under ordinary conditions become possible with those effects.
Interface is not only present between water and oil, but also in the boundaries between various immiscible substances. Foods that are generally composed of carbohydrates, proteins, fats and oils, water and air include various interfaces.
Surfactant for food is called food emulsifier which distinguishes it from other surfactants for industrial use.