Which two emulsifiers are commonly used to help stabilize emulsions in drinks?

• A. Vinegar and oil
• B. Egg white and lecithin
• C. Salt and sugar
• D. Water and ice

Answer: (B)

Emulsions stay stable when an ingredient sits at the oil–water interface and forms a protective film around droplets. Egg white provides proteins that readily adsorb to droplet surfaces, creating a barrier that helps prevent droplets from merging together. Lecithin, a phospholipid found in egg yolk and in some plants, is amphiphilic—one part loves water and one part loves oil—so it naturally positions itself at the interface and lowers interfacial tension, further stabilizing the mixture. These two are commonly used in drinks to keep oil droplets dispersed and to give a smoother texture.

Vinegar and oil don’t supply this kind of surface-stabilizing action; any mixture would separate again unless another emulsifier is present. Salt and sugar affect flavor and mouthfeel but don’t stabilize oil droplets. Water and ice are just forms of the same liquid and provide no interfacial stabilization.