Critical Review of Techniques and Methodologies for Characterization of Emulsion Stability

Mixture of 2 or more than liquids that are by and large immiscible

This commodity is almost mixtures of liquids. For the low-cal-sensitive mixture used in photography, see Photographic emulsion.

1. Two immiscible liquids, not yet emulsified
2. An emulsion of Stage 2 dispersed in Phase I
3. The unstable emulsion progressively separates
4. The surfactant (outline around particles) positions itself on the interfaces betwixt Phase Ii and Phase I, stabilizing the emulsion

An emulsion is a mixture of two or more than liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general course of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion should be used when both phases, dispersed and continuous, are liquids. In an emulsion, one liquid (the dispersed phase) is dispersed in the other (the continuous stage). Examples of emulsions include vinaigrettes, homogenized milk, liquid biomolecular condensates, and some cutting fluids for metal working.

Two liquids can form different types of emulsions. Every bit an example, oil and water tin form, first, an oil-in-water emulsion, in which the oil is the dispersed stage, and h2o is the continuous phase. 2nd, they can form a h2o-in-oil emulsion, in which water is the dispersed stage and oil is the continuous stage. Multiple emulsions are besides possible, including a "h2o-in-oil-in-h2o" emulsion and an "oil-in-water-in-oil" emulsion.^[1]

Emulsions, being liquids, do non showroom a static internal structure. The aerosol dispersed in the continuous phase (sometimes referred to as the "dispersion medium") are unremarkably assumed to exist statistically distributed to produce roughly spherical droplets.

The term "emulsion" is besides used to refer to the photo-sensitive side of photographic film. Such a photographic emulsion consists of silver halide colloidal particles dispersed in a gelatin matrix. Nuclear emulsions are similar to photographic emulsions, except that they are used in particle physics to observe high-energy simple particles.

Etymology [edit]

The word "emulsion" comes from the Latin emulgere "to milk out", from ex "out" + mulgere "to milk", as milk is an emulsion of fat and water, along with other components, including colloidal casein micelles (a type of secreted biomolecular condensate).^[two]

Appearance and backdrop [edit]

Fluid organisation in which liquid droplets are dispersed in a liquid.

Note 1: The definition is based on the definition in ref.^[3]

Note two: The droplets may be baggy, liquid-crystalline, or any
mixture thereof.

Note iii: The diameters of the droplets constituting the dispersed stage
usually range from approximately 10 nm to 100 μm; i.east., the droplets
may exceed the usual size limits for colloidal particles.

Note 4: An emulsion is termed an oil/water (o/due west) emulsion if the
dispersed stage is an organic material and the continuous phase is
water or an aqueous solution and is termed water/oil (w/o) if the dispersed
phase is water or an aqueous solution and the continuous phase is an
organic liquid (an "oil").

Note 5: A w/o emulsion is sometimes called an changed emulsion.
The term "inverse emulsion" is misleading, suggesting incorrectly that
the emulsion has properties that are the opposite of those of an emulsion.
Its use is, therefore, not recommended.^[4]

Emulsions incorporate both a dispersed and a continuous stage, with the boundary between the phases called the "interface".^[five] Emulsions tend to accept a cloudy appearance considering the many stage interfaces besprinkle light as it passes through the emulsion. Emulsions appear white when all light is scattered every bit. If the emulsion is dilute enough, higher-frequency (low-wavelength) lite will be scattered more, and the emulsion will announced bluer – this is called the "Tyndall result".^[6] If the emulsion is concentrated plenty, the colour will exist distorted toward comparatively longer wavelengths, and will appear more than yellow. This phenomenon is easily appreciable when comparing skimmed milk, which contains little fat, to cream, which contains a much higher concentration of milk fat. I example would be a mixture of h2o and oil.^[7]

Two special classes of emulsions – microemulsions and nanoemulsions, with droplet sizes beneath 100 nm – appear translucent.^[8] This property is due to the fact that light waves are scattered by the droplets only if their sizes exceed about one-quarter of the wavelength of the incident light. Since the visible spectrum of light is composed of wavelengths between 390 and 750 nanometers (nm), if the droplet sizes in the emulsion are beneath about 100 nm, the light can penetrate through the emulsion without beingness scattered.^[nine] Due to their similarity in appearance, translucent nanoemulsions and microemulsions are frequently confused. Dissimilar translucent nanoemulsions, which require specialized equipment to be produced, microemulsions are spontaneously formed by "solubilizing" oil molecules with a mixture of surfactants, co-surfactants, and co-solvents.^[8] The required surfactant concentration in a microemulsion is, however, several times higher than that in a translucent nanoemulsion, and significantly exceeds the concentration of the dispersed phase. Considering of many undesirable side-effects caused past surfactants, their presence is disadvantageous or prohibitive in many applications. In add-on, the stability of a microemulsion is oftentimes easily compromised by dilution, by heating, or by irresolute pH levels.^{[ citation needed ]}

Common emulsions are inherently unstable and, thus, do not tend to class spontaneously. Energy input – through shaking, stirring, homogenizing, or exposure to ability ultrasound^[x] – is needed to form an emulsion. Over fourth dimension, emulsions tend to revert to the stable state of the phases comprising the emulsion. An instance of this is seen in the separation of the oil and vinegar components of vinaigrette, an unstable emulsion that will quickly separate unless shaken almost continuously. There are important exceptions to this rule – microemulsions are thermodynamically stable, while translucent nanoemulsions are kinetically stable.^[8]

Whether an emulsion of oil and water turns into a "h2o-in-oil" emulsion or an "oil-in-h2o" emulsion depends on the book fraction of both phases and the blazon of emulsifier (surfactant) (encounter Emulsifier, below) present.^[11]

Instability [edit]

Emulsion stability refers to the ability of an emulsion to resist change in its backdrop over time.^{[12] [13]} At that place are four types of instability in emulsions: flocculation, coalescence, creaming/sedimentation, and Ostwald ripening. Flocculation occurs when at that place is an attractive forcefulness betwixt the droplets, and so they form flocs, like bunches of grapes. This process can be desired, if controlled in its extent, to melody physical properties of emulsions such every bit their catamenia behaviour. ^[14] Coalescence occurs when droplets bump into each other and combine to form a larger droplet, so the average droplet size increases over fourth dimension. Emulsions tin too undergo creaming, where the droplets rise to the height of the emulsion under the influence of buoyancy, or nether the influence of the centripetal strength induced when a centrifuge is used.^[12] Creaming is a common miracle in dairy and not-dairy beverages (i.e. milk, coffee milk, almond milk, soy milk) and usually does not change the droplet size.^[fifteen] Sedimentation is the contrary phenomenon of creaming and normally observed in water-in-oil emulsions.^[five] Sedimentation happens when the dispersed phase is denser than the continuous stage and the gravitational forces pull the denser globules towards the bottom of the emulsion. Similar to creaming, sedimentation follows Stokes' law.

An advisable "surface active agent" (or "surfactant") can increment the kinetic stability of an emulsion so that the size of the droplets does non change significantly with fourth dimension. The stability of an emulsion, like a suspension, tin can be studied in terms of zeta potential, which indicates the repulsion betwixt aerosol or particles. If the size and dispersion of droplets does not change over fourth dimension, it is said to exist stable.^[sixteen] For example, oil-in-water emulsions containing mono- and diglycerides and milk protein as surfactant showed that stable oil droplet size over 28 days storage at 25°C.^[xv]

Monitoring physical stability [edit]

The stability of emulsions can be characterized using techniques such as light scattering, focused beam reflectance measurement, centrifugation, and rheology. Each method has advantages and disadvantages.^[17]

Accelerating methods for shelf life prediction [edit]

The kinetic process of destabilization can be rather long – up to several months, or even years for some products.^[xviii] Often the formulator must accelerate this process in order to test products in a reasonable time during product design. Thermal methods are the virtually unremarkably used – these consist of increasing the emulsion temperature to advance destabilization (if beneath critical temperatures for phase inversion or chemical degradation).^[19] Temperature affects not just the viscosity but besides the interfacial tension in the case of non-ionic surfactants or, on a broader telescopic, interactions betwixt aerosol within the organisation. Storing an emulsion at loftier temperatures enables the simulation of realistic weather for a production (e.g., a tube of sunscreen emulsion in a motorcar in the summer rut), but also accelerates destabilization processes up to 200 times.^{[ citation needed ]}

Mechanical methods of acceleration, including vibration, centrifugation, and agitation, can besides exist used.^{[ citation needed ]}

These methods are almost always empirical, without a audio scientific basis.^{[ citation needed ]}

Emulsifiers [edit]

An emulsifier (too known equally an "emulgent") is a substance that stabilizes an emulsion by increasing its kinetic stability. Emulsifiers are a part of a broader group of compounds known as surfactants, or "surface-active agents".^[xx] Surfactants (emulsifiers) are compounds that are typically amphiphilic, significant they have a polar or hydrophilic (i.due east. h2o-soluble) part and a not-polar (i.e. hydrophobic or lipophilic) part. Considering of this, emulsifiers tend to have more or less solubility either in h2o or in oil.^{[ citation needed ]} Emulsifiers that are more soluble in water (and conversely, less soluble in oil) will generally form oil-in-h2o emulsions, while emulsifiers that are more than soluble in oil will form water-in-oil emulsions. ^[21]

Examples of nutrient emulsifiers are:

• Egg yolk – in which the main emulsifying and thickening agent is lecithin. In fact, lecithos is the Greek word for egg yolk.
• Mustard^[22] – where a variety of chemicals in the gum surrounding the seed hull human activity equally emulsifiers
• Soy lecithin is another emulsifier and thickener
• Pickering stabilization – uses particles under certain circumstances
• Sodium phosphates – not directly an emulsifier,^[23] just modifies behavior of other molecules, e.grand. casein
• Mono- and diglycerides – a common emulsifier found in many nutrient products (coffee creamers, water ice creams, spreads, breads, cakes)
• Sodium stearoyl lactylate
• DATEM (diacetyl tartaric acid esters of mono- and diglycerides) – an emulsifier used primarily in blistering
• Uncomplicated cellulose – a particulate emulsifier derived from institute fabric using only water
• Proteins – those with both hydrophilic and hydrophobic regions, east.k. sodium caseinate, every bit in meltable cheese product

Detergents are another class of surfactant, and volition interact physically with both oil and water, thus stabilizing the interface between the oil and h2o aerosol in suspension. This principle is exploited in soap, to remove grease for the purpose of cleaning. Many unlike emulsifiers are used in pharmacy to gear up emulsions such as creams and lotions. Common examples include emulsifying wax, polysorbate xx, and ceteareth 20.^[24]

Sometimes the inner stage itself can human activity as an emulsifier, and the result is a nanoemulsion, where the inner state disperses into "nano-size" droplets within the outer stage. A well-known example of this phenomenon, the "ouzo effect", happens when h2o is poured into a strong alcoholic anise-based drinkable, such as ouzo, pastis, absinthe, arak, or raki. The anisolic compounds, which are soluble in ethanol, then course nano-size droplets and emulsify inside the water. The resulting color of the drinkable is opaque and milky white.

Mechanisms of emulsification [edit]

A number of different chemical and physical processes and mechanisms can be involved in the process of emulsification:^[five]

• Surface tension theory – according to this theory, emulsification takes identify past reduction of interfacial tension between two phases
• Repulsion theory – the emulsifying agent creates a film over ane stage that forms globules, which repel each other. This repulsive force causes them to remain suspended in the dispersion medium
• Viscosity modification – emulgents similar acacia and tragacanth, which are hydrocolloids, besides as PEG (or polyethylene glycol), glycerine, and other polymers like CMC (carboxymethyl cellulose), all increment the viscosity of the medium, which helps create and maintain the suspension of globules of dispersed phase

Uses [edit]

In food [edit]

Oil-in-water emulsions are common in nutrient products:

• Crema (foam) in espresso – coffee oil in h2o (brewed coffee), unstable colloid
• Mayonnaise and Hollandaise sauces – these are oil-in-water emulsions stabilized with egg yolk lecithin, or with other types of nutrient additives, such as sodium stearoyl lactylate
• Homogenized milk – an emulsion of milk fatty in water, with milk proteins as the emulsifier
• Vinaigrette – an emulsion of vegetable oil in vinegar, if this is prepared using simply oil and vinegar (i.east., without an emulsifier), an unstable emulsion results

Water-in-oil emulsions are less mutual in food, simply still exist:

• Butter – an emulsion of h2o in butterfat
• Margarine

Other foods can be turned into products similar to emulsions, for example meat emulsion is a suspension of meat in liquid that is similar to truthful emulsions.

In health care [edit]

In pharmaceutics, hairstyling, personal hygiene, and cosmetics, emulsions are frequently used. These are usually oil and h2o emulsions but dispersed, and which is continuous depends in many cases on the pharmaceutical formulation. These emulsions may exist chosen creams, ointments, liniments (balms), pastes, films, or liquids, depending mostly on their oil-to-water ratios, other additives, and their intended route of administration.^{[25] [26]} The showtime five are topical dosage forms, and may be used on the surface of the skin, transdermally, ophthalmically, rectally, or vaginally. A highly liquid emulsion may likewise be used orally, or may exist injected in some cases.^[25]

Microemulsions are used to deliver vaccines and kill microbes.^[27] Typical emulsions used in these techniques are nanoemulsions of soybean oil, with particles that are 400–600 nm in diameter.^[28] The process is non chemical, as with other types of antimicrobial treatments, but mechanical. The smaller the droplet the greater the surface tension and thus the greater the force required to merge with other lipids. The oil is emulsified with detergents using a high-shear mixer to stabilize the emulsion so, when they encounter the lipids in the cell membrane or envelope of leaner or viruses, they force the lipids to merge with themselves. On a mass scale, in effect this disintegrates the membrane and kills the pathogen. The soybean oil emulsion does non harm normal human cells, or the cells of most other college organisms, with the exceptions of sperm cells and blood cells, which are vulnerable to nanoemulsions due to the peculiarities of their membrane structures. For this reason, these nanoemulsions are not currently used intravenously (IV). The nigh effective awarding of this type of nanoemulsion is for the disinfection of surfaces. Some types of nanoemulsions have been shown to finer destroy HIV-i and tuberculosis pathogens on non-porous surfaces.

In firefighting [edit]

Emulsifying agents are effective at extinguishing fires on small-scale, thin-layer spills of combustible liquids (course B fires). Such agents encapsulate the fuel in a fuel-water emulsion, thereby trapping the flammable vapors in the water phase. This emulsion is accomplished by applying an aqueous surfactant solution to the fuel through a high-pressure nozzle. Emulsifiers are not effective at extinguishing large fires involving majority/deep liquid fuels, because the amount of emulsifier amanuensis needed for extinguishment is a function of the book of the fuel, whereas other agents such as aqueous flick-forming foam need comprehend only the surface of the fuel to achieve vapor mitigation.^[29]

Chemical synthesis [edit]

Emulsions are used to manufacture polymer dispersions – polymer production in an emulsion 'phase' has a number of procedure advantages, including prevention of coagulation of production. Products produced by such polymerisations may be used equally the emulsions – products including main components for glues and paints. Constructed latexes (rubbers) are besides produced by this process.

Meet likewise [edit]

• Emulsion dispersion
• Emulsified fuel
• Homogenizer
• Liquid whistle
• Miniemulsion
• Pickering emulsion
• Rheology
• Water-in-water emulsion

References [edit]

1. ^ Khan, A. Y.; Talegaonkar, S; Iqbal, Z; Ahmed, F. J.; Khar, R. K. (2006). "Multiple emulsions: An overview". Current Drug Delivery. three (iv): 429–43. doi:10.2174/156720106778559056. PMID 17076645.
2. ^ Harper, Douglas. "Online Etymology Dictionary". www..etymonline.com. Etymonline. Retrieved 2 November 2019.
3. ^ IUPAC (1997). "Emulsion". Compendium of Chemical Terminology (The "Gold Book"). Oxford: Blackwell Scientific Publications. doi:10.1351/goldbook.E02065. ISBN978-0-9678550-9-7. Archived from the original on 2012-03-10. {{cite book}}: CS1 maint: bot: original URL status unknown (link)
4. ^ Slomkowski, Stanislaw; Alemán, José Five.; Gilbert, Robert G.; Hess, Michael; Horie, Kazuyuki; Jones, Richard 1000.; Kubisa, Przemyslaw; Meisel, Ingrid; Mormann, Werner; Penczek, Stanisław; Stepto, Robert F. T. (2011). "Terminology of polymers and polymerization processes in dispersed systems (IUPAC Recommendations 2011)" (PDF). Pure and Applied Chemical science. 83 (12): 2229–2259. doi:10.1351/PAC-REC-10-06-03. S2CID 96812603.
5. ^ ^{a b c} Loi, Chia Chun; Eyres, Graham T.; Birch, Eastward. John (2018), "Poly peptide-Stabilised Emulsions", Reference Module in Food Science, Elsevier, doi:10.1016/b978-0-08-100596-5.22490-6, ISBN9780081005965
6. ^ Joseph Price Remington (1990). Alfonso R. Gennaro (ed.). Remington'due south Pharmaceutical Sciences. Mack Publishing Company (Original from Northwestern University) (Digitized 2010). p. 281. ISBN9780912734040.
7. ^ "Emulsion - an overview | ScienceDirect Topics". www.sciencedirect.com . Retrieved 2022-03-01 .
8. ^ ^{a b c} Bricklayer TG, Wilking JN, Meleson K, Chang CB, Graves SM (2006). "Nanoemulsions: Formation, construction, and physical properties" (PDF). Periodical of Physics: Condensed Affair. xviii (41): R635–R666. Bibcode:2006JPCM...18R.635M. doi:x.1088/0953-8984/18/41/R01. Archived from the original (PDF) on 2017-01-12. Retrieved 2016-10-26 .
9. ^ Leong TS, Wooster TJ, Kentish SE, Ashokkumar M (2009). "Minimising oil droplet size using ultrasonic emulsification" (PDF). Ultrasonics Sonochemistry. sixteen (6): 721–vii. doi:10.1016/j.ultsonch.2009.02.008. hdl:11343/129835. PMID 19321375.
10. ^ Kentish, S.; Wooster, T.J.; Ashokkumar, One thousand.; Balachandran, S.; Mawson, R.; Simons, Fifty. (2008). "The use of ultrasonics for nanoemulsion training". Innovative Food Science & Emerging Technologies. ix (2): 170–175. doi:10.1016/j.ifset.2007.07.005. hdl:11343/55431.
11. ^ "Emulsion - an overview | ScienceDirect Topics".
12. ^ ^{a b} McClements, David Julian (16 Dec 2004). Food Emulsions: Principles, Practices, and Techniques, 2d Edition. Taylor & Francis. pp. 269–. ISBN978-0-8493-2023-i.
13. ^ Silvestre, M.P.C.; Decker, Due east.A.; McClements, D.J. (1999). "Influence of copper on the stability of whey protein stabilized emulsions". Food Hydrocolloids. 13 (5): 419. doi:ten.1016/S0268-005X(99)00027-two.
14. ^ Fuhrmann, Philipp L.; Sala, Guido; Stieger, Markus; Scholten, Elke (2019-08-01). "Clustering of oil droplets in o/w emulsions: Controlling cluster size and interaction force". Food Research International. 122: 537–547. doi:10.1016/j.foodres.2019.04.027. ISSN 0963-9969. PMID 31229109.
15. ^ ^{a b} Loi, Chia Chun; Eyres, Graham T.; Birch, Due east. John (2019). "Effect of mono- and diglycerides on concrete properties and stability of a poly peptide-stabilised oil-in-water emulsion". Periodical of Food Applied science. 240: 56–64. doi:10.1016/j.jfoodeng.2018.07.016. ISSN 0260-8774. S2CID 106021441.
16. ^ Mcclements, David Julian (2007-09-27). "Critical Review of Techniques and Methodologies for Label of Emulsion Stability". Critical Reviews in Food Scientific discipline and Diet. 47 (7): 611–649. doi:10.1080/10408390701289292. ISSN 1040-8398. PMID 17943495. S2CID 37152866.
17. ^ Dowding, Peter J.; Goodwin, James W.; Vincent, Brian (2001-11-xxx). "Factors governing emulsion droplet and solid particle size measurements performed using the focused beam reflectance technique". Colloids and Surfaces A: Physicochemical and Engineering Aspects. 192 (i): 5–thirteen. doi:10.1016/S0927-7757(01)00711-7. ISSN 0927-7757.
18. ^ Dickinson, Eric (1993). "Emulsion Stability". In Nishinari, Katsuyoshi; Doi, Etsushiro (eds.). Nutrient Hydrocolloids. Nutrient Hydrocolloids: Structures, Properties, and Functions. Springer US. pp. 387–398. doi:10.1007/978-ane-4615-2486-1_61. ISBN9781461524861.
19. ^ Masmoudi, H.; Dréau, Y. Le; Piccerelle, P.; Kister, J. (2005-01-31). "The evaluation of cosmetic and pharmaceutical emulsions crumbling process using classical techniques and a new method: FTIR" (PDF). International Journal of Pharmaceutics. 289 (1): 117–131. doi:10.1016/j.ijpharm.2004.ten.020. ISSN 0378-5173. PMID 15652205.
20. ^ "Emulsions: making oil and water mix". world wide web.aocs.org . Retrieved 1 Jan 2021.
21. ^ Cassidy, L. (n.d.). Emulsions: Making oil and water mix. Retrieved from https://www.aocs.org/stay-informed/inform-magazine/featured-articles/emulsions-making-oil-and-h2o-mix-april-2014
22. ^ Riva Pomerantz (Nov fifteen, 2017). "KOSHER IN THE LAB". Ami. No. 342.
23. ^ John R. Sevenich (1993-11-08). Quote: 'Sodium phosphates are not emulsifiers in the strict sense, i.east. they are non surface-active substances, nonetheless they are commonly included in the group of ingredients called "emulsifying agents". (See Caric et al., Food Microstructure, Vol. 4, pgs. 297-312 (1985).' US patent № 5,466,477 — Preparation of process cheese using liquid sodium phosphate
24. ^ Anne-Marie Faiola (2008-05-21). "Using Emulsifying Wax". TeachSoap.com. TeachSoap.com. Retrieved 2008-07-22 .
25. ^ ^{a b} Aulton, Michael E., ed. (2007). Aulton's Pharmaceutics: The Blueprint and Industry of Medicines (3rd ed.). Churchill Livingstone. pp. 92–97, 384, 390–405, 566–69, 573–74, 589–96, 609–10, 611. ISBN978-0-443-10108-3.
26. ^ Troy, David A.; Remington, Joseph P.; Beringer, Paul (2006). Remington: The Science and Practice of Pharmacy (21st ed.). Philadelphia: Lippincott Williams & Wilkins. pp. 325–336, 886–87. ISBN978-0-7817-4673-ane.
27. ^ "Adjuvant Vaccine Development". Archived from the original on 2008-07-05. Retrieved 2008-07-23 .
28. ^ "Nanoemulsion vaccines testify increasing promise". Eurekalert! Public News List. University of Michigan Health Organisation. 2008-02-26. Retrieved 2008-07-22 .
29. ^ Friedman, Raymond (1998). Principles of Burn Protection Chemistry and Physics. Jones & Bartlett Learning. ISBN978-0-87765-440-7.

Other sources [edit]

• Philip Sherman; British Society of Rheology (1963). Rheology of emulsions: proceedings of a symposium held by the British Society of Rheology ... Harrogate, October 1962. Macmillan. ISBN9780080102900.
• Handbook of Nanostructured Materials and Nanotechnology; Nalwa, H.S., Ed.; Academic Press: New York, NY, USA, 2000; Volume v, pp. 501–575

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Source: https://en.wikipedia.org/wiki/Emulsion

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