Emulsion

An emulsion is a mixture in which droplets of one liquid are dispersed throughout another liquid that does not normally mix with it, such as oil and water. In cooking, emulsions are used to create sauces, dressings, dairy products and other preparations with a smooth, unified texture. Some emulsions are temporary, while others are stabilized by emulsifiers or the structure of the ingredients.

Types of culinary emulsion

• Oil-in-water: oil droplets are dispersed in a water-based phase. Mayonnaise is a classic example.
• Water-in-oil: water droplets are dispersed in a continuous fat phase. Butter is a common example.
• Temporary emulsion: a vinaigrette that separates after standing but can be remixed.
• Stabilized emulsion: mayonnaise, where egg-yolk emulsifiers help keep oil droplets dispersed.
• Warm emulsion: hollandaise, béarnaise and beurre blanc, which require temperature control to remain smooth.

What stabilizes an emulsion?

Mechanical action breaks one liquid into small droplets. Emulsifiers such as lecithin in egg yolk help reduce the tendency of droplets to merge. The stability also depends on droplet size, ingredient ratio, temperature, acidity and the viscosity of the continuous phase.

Emulsion versus suspension

An emulsion contains droplets of one liquid dispersed in another. A suspension contains solid particles distributed through a liquid. A spice or flour mixture in water is not necessarily an emulsion.

Chef’s tip: Add the dispersed liquid gradually and control the temperature. If a sauce splits, stop adding fat and rebuild the mixture using the appropriate aqueous phase or emulsifier.

Key distinction: An emulsion is a dispersed system of immiscible liquids; it is not a solution in which one liquid has dissolved completely in another.