coemulsifiers

Coemulsifiers are substances used in emulsion systems to assist primary emulsifiers in stabilizing mixtures of immiscible liquids. They are called coemulsifiers or co-emulsifiers and are commonly used in cosmetics, pharmaceuticals, and food products to enhance stability, texture, and performance of emulsions such as creams and lotions.

Coemulsifiers work by accompanying the main emulsifier at the oil–water interface, helping to form a more cohesive interfacial film, reducing interfacial tension, and enabling more uniform droplet sizes. They can modify the rheology of the continuous phase and improve resistance to phase separation under varying temperature, electrolytes, or mechanical stress.

Types of coemulsifiers include fatty alcohols, glyceryl esters, and other amphiphilic additives that are compatible with the primary system. They are chosen to complement the emulsifier system and can influence feel, spreadability, and appearance. They are not standalone primary emulsifiers but support the performance of the main surfactants.

In topical cosmetic emulsions, coemulsifiers help achieve stable water-in-oil or oil-in-water creams with desirable texture. They are also used in some pharmaceutical gels and foods as part of a multi-component emulsifier system, contributing to stability and sensory properties in certain products.

Formulators consider compatibility with the primary emulsifier, desired rheology, pH and ionic conditions, regulatory status, and sensory properties. Small changes can affect stability, phase behavior, and shelf life.