AskDefine | Define emulsifier

Dictionary Definition

emulsifier n : a surface-active agent that promotes the formation of an emulsion

User Contributed Dictionary

English

Pronunciation

  • a UK /ˈɪi.mʌl.sɪf.aɪ.ə(ɹ)/|/əˈmʌl.sɪf.aɪ.ə(ɹ)/; /"i:.mVl.sIf.aI.@(r)/|/@"mVl.sIf.aI.@(r)/

Noun

  1. A substance that helps an emulsion form, or helps keep an emulsion from separating.

Antonyms

Extensive Definition

Used in pharmaceuticals and in cosmetics(skin care)
An emulsion(IPA: /ɪˈmʌlʃən/) is a mixture of two immiscible (unblendable) substances. One substance (the dispersed phase) is dispersed in the other (the continuous phase). Examples of emulsions include butter and margarine, milk and cream, espresso, mayonnaise, the photo-sensitive side of photographic film, magmas and cutting fluid for metal working. In butter and margarine, oil surrounds droplets of water (a water-in-oil emulsion). In milk and cream, water surrounds droplets of oil (an oil-in-water emulsion). In certain types of magma, globules of liquid NiFe may be dispersed within a continuous phase of liquid silicates. Emulsification is the process by which emulsions are prepared.
Emulsion is also a term used in the oil field as untreated well production that consists primarily of crude oil and water.

Operation

Emulsions tend to have a cloudy appearance, because the many phase interfaces (the boundary between the phases is called the interface) scatter light that passes through the emulsion. Emulsions are unstable and thus do not form spontaneously. Energy input through shaking, stirring, homogenizers, or spray processes are needed to form an emulsion. Over time, emulsions tend to revert to the stable state of oil separated from water. Surface active substances (surfactants) can increase the kinetic stability of emulsions greatly so that, once formed, the emulsion does not change significantly over years of storage. Homemade oil and vinegar salad dressing is an example of an unstable emulsion that will quickly separate unless shaken continuously. This phenomenon is called coalescence, and happens when small droplets recombine to form bigger ones. Fluid emulsions can also suffer from creaming, the migration of one of the substances to the top of the emulsion under the influence of buoyancy or centripetal force when a centrifuge is used.
Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion tends to imply that both the dispersed and the continuous phase are liquid.
There are three types of emulsion instability: flocculation, where the particles form clumps; creaming, where the particles concentrate towards the surface (or bottom, depending on the relative density of the two phases) of the mixture while staying separated; and breaking and coalescence where the particles coalesce and form a layer of liquid.

Emulsifier

An emulsifier (also known as an emulgent) is a substance which stabilizes an emulsion, frequently a surfactant. Examples of food emulsifiers are egg yolk (where the main emulsifying chemical is lecithin), honey and mustard, where a variety of chemicals in the mucilage surrounding the seed hull act as emulsifiers; proteins and low-molecular weight emulsifiers are common as well. In some cases, particles can stabilize emulsions as well through a mechanism called Pickering stabilization. Both mayonnaise and hollandaise sauce are oil-in-water emulsions that are stabilized with egg yolk lecithin. Detergents are another class of surfactant, and will chemically interact with both oil and water, thus stabilising the interface between oil or water droplets in suspension. This principle is exploited in soap to remove grease for the purpose of cleaning. A wide variety of emulsifiers are used in pharmacy to prepare emulsions such as creams and lotions.

References

emulsifier in Bosnian: Emulzija
emulsifier in Catalan: Emulsió
emulsifier in Czech: Emulze
emulsifier in Danish: Emulsion
emulsifier in German: Emulsion
emulsifier in Estonian: Emulsioon
emulsifier in Spanish: Emulsión
emulsifier in French: Émulsion
emulsifier in Galician: Emulsión
emulsifier in Croatian: Emulzija
emulsifier in Indonesian: Emulsi
emulsifier in Italian: Emulsione
emulsifier in Hebrew: חומר מתחלב
emulsifier in Malay (macrolanguage): Emulsi
emulsifier in Dutch: Emulsie
emulsifier in Japanese: エマルション
emulsifier in Norwegian: Emulsjon
emulsifier in Polish: Emulsja
emulsifier in Portuguese: Emulsão
emulsifier in Romanian: Emulsie
emulsifier in Russian: Эмульсия
emulsifier in Slovenian: Emulzija
emulsifier in Serbian: Емулзија
emulsifier in Serbo-Croatian: Emulzija
emulsifier in Finnish: Emulsio
emulsifier in Swedish: Emulsion
emulsifier in Vietnamese: Nhũ tương
emulsifier in Thai: อิมัลชัน
emulsifier in Turkish: Emülsiyon
emulsifier in Ukrainian: Емульсія
emulsifier in Chinese: 乳剂
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