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Information about Emulsion

A. Two immiscible liquids, not emulsified; B. An emulsion of Phase II dispersed in Phase I; C. The unstable emulsion progressively separates; D. The surfactant (purple outline) positions itself on the interfaces between Phase A and Phase B, stabilizing the emulsion


An emulsion 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, espresso, mayonnaise, the photo-sensitive side of photographic film, and cutting fluid for metal working. In butter and margarine, a continuous liquid phase surrounds droplets of water (water-in-oil emulsion). Emulsification is the process by which emulsions are prepared.

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.

Emulsion is also a term used in the oil field as untreated well production that consists primarily of crude oil and water.

Nanoemulsion

Nanoemulsion is a type of emulsion in which the sizes of the particles in the dispersed phase are defined as less than 1000 nanometers.

In medicine, a nanoemulsion of soybean oil to create drops of 400-600 nanometers in diameter will kill many pathogens such as bacteria and viruses. The process is not chemical, as with other types of anti-pathogenic treatments, but physical. The smaller the droplet, the greater the surface tension and thus the greater the force to merge with other lipids. The oil is emulsified with detergents to stabilize the emulsion (the droplets won't merge with one another), so when they encounter lipids on a bacterial membrane or a virus envelope, they force the lipids to merge with themselves. On a mass scale, this effectively disintegrates the membrane and kills the pathogen.

Remarkably, the soybean oil emulsion does not harm normal human cells nor the cells of most other higher organisms. The exceptions are sperm cells and blood cells, which are vulnerable to nanoemulsions due to their membrane structures. For this reason, nanoemulsions of this type are not yet ready to be used intravenously.

The most effective application of this type of nanoemulsion is for the disinfection of surfaces. Some types of nanoemulsions have been shown to effectively destroy HIV-1 and various tuberculosis pathogens, for example, on non-porous surfaces.

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 the phospholipid lecithin), 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.
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20 ml ampule of 1% propofol emulsion suitable for intravenous injection. The manufacturers emulsify the lipid soluble propofol in a mixture of water, soy oil and egg lecithin.


Whether an emulsion turns into a water-in-oil emulsion or an oil-in-water emulsion depends on the volume fraction of both phases and on the type of emulsifier. Generally, the Bancroft rule applies: emulsifiers and emulsifying particles tend to promote dispersion of the phase in which they do not dissolve very well; for example, proteins dissolve better in water than in oil and so tend to form oil-in-water emulsions (that is they promote the dispersion of oil droplets throughout a continuous phase of water).

See also

External links

References

Category

Interface and Colloid Science
Miscibility is a term in chemistry that refers to the property of liquids to mix in all proportions, forming a homogeneous solution. In principle, the term applies also to other phases (solids and gases), but the main focus on the solubility of one liquid in another.
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In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i.e. density, crystal structure, index of refraction, and so forth).
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Dispersion can refer to:
  • Biological dispersal, the distribution of spores, fruits and their seeds, etc.
  • A phenomenon that causes the separation of a wave into components of varying frequency:

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In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i.e. density, crystal structure, index of refraction, and so forth).
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Butter is a dairy product, made by churning fresh or fermented cream or milk. Butter is used as a spread and a condiment, as well as in cooking applications such as baking, sauce making, and frying.
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Margarine (pronounced IPA: /ˈmɑrdʒərɪn, ˈmɑrgəriːn/), as a generic term, can indicate any of a wide range of butter substitutes.
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Espresso or caffè espresso is a concentrated coffee beverage brewed by forcing very hot, but not boiling water under high pressure through coffee that has been ground to a consistency between extremely fine and powder.
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Mayonnaise (or Mayo in its abbreviated form) is a thick sauce made primarily from vegetable oil and egg yolks.[1] Whitish-yellow in color, it is a stable emulsion formed from the oil and the yolks and is generally flavored with mustard, lemon juice and/or vinegar,
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Photographic film is a sheet of plastic (polyester, nitrocellulose or cellulose acetate) coated with an emulsion containing light-sensitive silver halide salts (bonded by gelatin) with variable crystal sizes that determine the sensitivity, contrast and resolution of the film.
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Cutting fluid or coolant is a liquid added to reduce the friction coefficient between the grain and workpiece by way of cooling and lubricating the cutting site of machine tools by flooding or spraying during broaching, boring, grinding, milling, sawing, shaping or tapping.
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In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i.e. density, crystal structure, index of refraction, and so forth).
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Scattering is a general physical process whereby some forms of radiation, such as light, sound or moving particles, for example, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which it passes.
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Surfactants, also known as tensides, are wetting agents that lower the surface tension of a liquid, allowing easier spreading, and lower the interfacial tension between two liquids.
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Cooking oil is purified fat of plant or animal origin, which is liquid at room temperature.

Some of the many different kinds of edible vegetable oils include: olive oil, palm oil, soybean oil, canola oil, pumpkin seed oil, corn oil, sunflower oil, safflower oil, peanut oil,
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Vinegar is a liquid produced from the fermentation of ethanol in a process that yields its key ingredient, acetic acid. The acetic acid concentration ranges typically from 4 to 8 percent by volume for table vinegar[1]
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For other uses, see Coalescence (disambiguation).


Coalescence is the process by which two or more droplets or particles merge during contact to form a single daughter droplet (or bubble).
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Creaming, in cooking, is the technique of blending ingredients — usually granulated sugar — together with a solid fat like shortening or butter. The technique is most often used in making cake batter or cookie dough.
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In physics, buoyancy is the upward force on an object produced by the surrounding fluid (i.e., a liquid or a gas) in which it is fully, or partially immersed, due to the pressure difference of the fluid between the top and bottom of the object.
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centripetal force is the external force required to make a body follow a circular path at constant speed (speed being the magnitude of velocity). The force is directed inward, toward the center of the circle. Hence it is a force requirement, not a particular kind of force.
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centrifuge is a piece of equipment, generally driven by a motor, that puts an object in rotation around a fixed axis, applying force perpendicular to the axis. The centrifuge works using the sedimentation principle, where the centripetal acceleration is used to separate substances
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A Colloid or colloidal dispersion is a type of heterogeneous mixture. A colloid consists of two separate phases: a dispersed and balls phase and a continuous phase. In a colloid, the dispersed phase is made of tiny particles or droplets that are distributed evenly throughout
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Liquid is one of the four principal states of matter. A liquid is a fluid that can freely form a distinct surface at the boundaries of its bulk material.

Characteristics

A liquid's shape is determined by, not confined to, the container it fills.
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Flocculation is a process where a solute comes out of solution in the form of floc or "flakes." The term is also used to refer to the process by which fine particulates are caused to clump together into floc.
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Creaming, in cooking, is the technique of blending ingredients — usually granulated sugar — together with a solid fat like shortening or butter. The technique is most often used in making cake batter or cookie dough.
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Coalescence may refer to:
  • Coalescence (genetics), the merging of lineages in backwards time
  • Coalescence (linguistics), the merging of two or more words merge into one
  • Coalescence (meteorology), the merging of two or more droplets into one

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1 metre =
SI units
1000 mm 0 cm
US customary / Imperial units
0 ft 0 in
The metre or meter[1](symbol: m) is the fundamental unit of length in the International System of Units (SI).
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A pathogen or infectious agent is a biological agent that causes disease or illness to its host.[1] The term is most often used for agents that disrupt the normal physiology of a multicellular animal or plant.
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Surface tension is an effect within the surface layer of a liquid that causes that layer to behave as an elastic sheet. It allows insects, such as the water strider (pond skater, UK), to walk on water.
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Lipids can be broadly defined as any fat-soluble (hydrophobic), naturally-occurring molecules. The term is more-specifically used to refer to fatty-acids and their derivatives (including tri-, di-, and monoglycerides and phospholipids) as well as other fat-soluble sterol-containing
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