Science, Tech, Math › Science Emulsifier Definition: Emulsifying Agent Emulsifiers in Chemistry Share Flipboard Email Print Egg yolks are the emulsifier in mayonnaise. milanfoto / Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated December 01, 2019 Emulsifier Definition An emulsifier or emulsifying agent is a compound or substance that acts as a stabilizer for emulsions, preventing liquids that ordinarily don't mix from separating. The word comes from the Latin word meaning "to milk," in reference to milk as an emulsion of water and fat. Another word for an emulsifier is an emulgent. The term emulsifier may also refer to an apparatus that shakes or stirs ingredients to form an emulsion. How an Emulsifier Works An emulsifier keeps immiscible compounds from separating by increasing the kinetic stability of the mixture. Surfactants are one class of emulsifiers, which lower surface tension between liquids or between a solid and liquid. Surfactants keep droplets from getting large enough for components to be able to separate based on density. The method of emulsification matters in addition to the nature of the emulsifier. Proper integration of components extends the emulsion's ability to resist changes. For example, if you are making an emulsion for cooking, the mixture will maintain its properties longer if you use a blender than if you stir the ingredients by hand. Emulsifier Examples Egg yolks are used as an emulsifier in mayonnaise to keep the oil from separating out. The emulsifying agent in egg yolks is lecithin. Mustard contains multiple chemicals in the mucilage around the seed that act together as emulsifiers. Other examples of emulsifiers include sodium phosphates, sodium stearoyl lactylate, soy lecithin, Pickering stabilization, and DATEM (diacetyl tartaric acid ester of monoglyceride). Homogenized milk, vinaigrettes, and metalworking cutting fluids are examples of common emulsions.