Fundamentals of Food Technology

Emulsion

Definition

When a liquid, e.g., oil is dispersed in another immiscible liquid, e.g., water (continuous phase) by mechanical agitation, an emulsion is obtained.

Emulsifying agent
An emulsifying agent is a surface active agent that lowers the interfacial tension and forms a physical barrier around each droplet of the dispersed phase.

Types of emulsion
Oil in water emulsion
Where the dispersed phase consists of droplets of oil dispersed in the continuous phase which is mainly water.
eg. Salad oil, Mayonnaise, milk, beverages, cream soups and ice-creams.

Water in oil emulsion
Where the dispersed phase consists of droplets of water dispersed in the continuous phase which is mainly oil.
eg: Butter, margarine and egg yolk.

Multiple emulsions
The fat content of food emulsion like water in oil can be reduced by replacing some fat inside the oil droplets with small water droplets.

Water multiple emulsions
The substance within the droplets is referred to as the dispersed or internal phase, where as the substances that makes up the surrounding liquid is called continuous or external phase.

Foam

"Foam is a dispersion of gas bubbles in a liquid or semi solid phase".
Because of the foaming nature, the bubbles are separated from each other by liquid or semisolid wall also called film or lamellae that are elastic stable foams. The diameter of air bubbles varies widely.