Types of Emulsions

Emulsions can be temporary, semipermanent, or permanent and differ in their degree of viscosity and stability. Stability is defined by the degree to which the liquids stay in emulsion regardless of gravity, agitation, long storage times, extreme temperatures, surface drying, or added salt.

Temporary Emulsions

Temporary emulsions are the least viscous and stable, separating on standing, a process called creaming. Such temporary emulsions include oil and vinegar salad dressings, in which the oil rises to the top of the vinegar. These emulsions must be shaken each time they are used in order to reform the emulsion.

Semipermanent Emulsions

Stabilizers may be added to an emulsion to decrease the tendency of the emulsion to separate, which creates a viscosity similar to soft yogurt. Semipermanent emulsions include commercial French and Italian salad dressings.

Permanent Emulsions

Permanent emulsions are very viscous and stable, to the point that they do not separate. Mayonnaise is a permanent emulsion in which the major ingredient is vegetable oil (dispersed phase). The added egg yolk in mayonnaise contains lecithin, which acts as an emulsifier to keep the oil dispersed in the liquid, usually vinegar or lemon (continuous phase). The high oil content of mayonnaise contributes about 100 calories (kcal) and 11 grams of fat in every tablespoon. Lower-fat alternatives are available, however.