Casein ( / ˈ k eɪ s iː n / KAY -seen , from Latin caseus "cheese") is a family of related phosphoproteins ( αS1 , aS2, β , κ ) that are commonly found in mammalian milk , comprising about 80% of the proteins in cow's milk and between 20% and 60% of the proteins in human milk . Sheep and cow milk have a higher casein content than other types of milk with human milk having a particularly low casein content.
60-426: Casein is the primary emulsifier in milk, that is, it helps in mixing oils, fats, and water in milk. Casein has a wide variety of uses, from being a major component of cheese , to use as a food additive. The most common form of casein is sodium caseinate (historically called nutrose ), which is a very efficient emulsifier. Casein is secreted into milk from mammary cells in the form of colloidal casein micelles ,
120-423: A casein-free diet has been shown to improve outcomes of infants who are breastfed while allergic or intolerant to dairy protein. Human breast milk has been proven to be the best food for an infant, and should be tried first where available. Supplementation of protease enzyme has been shown to help casein intolerant individuals digest the protein with minimal adverse reaction. Emulsifier An emulsion
180-728: A suspension , can be studied in terms of zeta potential , which indicates the repulsion between droplets or particles. If the size and dispersion of droplets does not change over time, it is said to be stable. 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. 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. The kinetic process of destabilization can be rather long – up to several months, or even years for some products. Often
240-447: A "water-in-oil" emulsion or an "oil-in-water" emulsion depends on the volume fraction of both phases and the type of emulsifier (surfactant) (see Emulsifier , below) present. Emulsion stability refers to the ability of an emulsion to resist change in its properties over time. There are four types of instability in emulsions: flocculation , coalescence , creaming / sedimentation , and Ostwald ripening . Flocculation occurs when there
300-411: A mixture of surfactants , co-surfactants, and co- solvents . 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. Because of many undesirable side-effects caused by surfactants, their presence is disadvantageous or prohibitive in many applications. In addition,
360-538: A number of process advantages, including prevention of coagulation of product. Products produced by such polymerisations may be used as the emulsions – products including primary components for glues and paints. Synthetic latexes (rubbers) are also produced by this process. Polyvinyl acetate Polyvinyl acetate ( PVA , PVAc , poly(ethenyl ethanoate) ), commonly known as wood glue (a term that may also refer to other types of glues ), PVA glue , white glue , carpenter's glue , school glue , or Elmer's Glue in
420-523: A product in the early 1920s named Casec to ease gastrointestinal disorders and infant digestive problems which were a common cause of death in children at that time. All caseinates have very efficient emulsifying properties and widely used to make emulsions in foods. It is believed to neutralize capsaicin , the active ingredient of chili peppers such as jalapeños , and habaneros . Milk is often consumed to decrease irritation caused by spicy foods. Cheese consists of proteins and fat from milk , usually
480-695: A sound scientific basis. An emulsifier is a substance that stabilizes an emulsion by reducing the oil-water interface tension . Emulsifiers are a part of a broader group of compounds known as surfactants , or "surface-active agents". Surfactants are compounds that are typically amphiphilic , meaning they have a polar or hydrophilic (i.e., water-soluble) part and a non-polar (i.e., hydrophobic or lipophilic ) part. Emulsifiers that are more soluble in water (and, conversely, less soluble in oil) will generally form oil-in-water emulsions, while emulsifiers that are more soluble in oil will form water-in-oil emulsions. Examples of food emulsifiers are: In food emulsions,
540-399: A type of biomolecular condensate . As a food source , casein supplies amino acids , carbohydrates , and two essential elements, calcium and phosphorus . Casein contains a high number of proline amino acids which hinder the formation of common secondary structural motifs of proteins. There are also no disulfide bridges . As a result, it has relatively little tertiary structure . It
600-696: A use in certain niche applications, such as laminating fireproof doors and the labeling of bottles. Casein glues thin rapidly with increasing temperature, making it easy to apply thin films quickly to label jars and bottles on a production line. Several foods, creams, and toppings all contain a variety of caseinates. Sodium caseinate acts as a greater food additive for stabilizing processed foods; however, companies could opt to use calcium caseinate to increase calcium content and decrease sodium levels in their products. The main food uses of casein are for powders requiring rapid dispersion into water, ranging from coffee creamers to instant cream soups. Mead Johnson introduced
660-503: A water-in-oil emulsion, in which water is the dispersed phase and oil is the continuous phase. Multiple emulsions are also possible, including a "water-in-oil-in-water" emulsion and an "oil-in-water-in-oil" emulsion. Emulsions, being liquids, do not exhibit a static internal structure. The droplets dispersed in the continuous phase (sometimes referred to as the "dispersion medium") are usually assumed to be statistically distributed to produce roughly spherical droplets. The term "emulsion"
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#1732851453279720-422: Is dispersed in the other (the continuous phase). 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. As an example, oil and water can form, first, an oil-in-water emulsion, in which the oil is the dispersed phase, and water is the continuous phase. Second, they can form
780-449: Is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation . 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 should be used when both phases, dispersed and continuous, are liquids. In an emulsion, one liquid (the dispersed phase )
840-418: Is a vinyl polymer . Polyvinyl acetate is prepared by the polymerization of vinyl acetate monomer ( free-radical vinyl polymerization of the monomer vinyl acetate). As a dispersion in water (usually an emulsion), PVAc preparations are used as adhesives for porous materials, particularly for wood , paper , and cloth , and as a consolidant for porous building stone, in particular sandstone . PVAc
900-445: Is able to provide a sustained slow release of amino acids into the blood stream, sometimes lasting for several hours. Often casein is available as hydrolyzed casein , whereby it is hydrolyzed by a protease such as trypsin . Hydrolyzed forms are noted to taste bitter and such supplements are often refused by infants and lab animals in favor of intact casein. Some of the earliest plastics were based on casein. In particular, galalith
960-531: Is achieved by applying an aqueous surfactant solution to the fuel through a high-pressure nozzle. Emulsifiers are not effective at extinguishing large fires involving bulk/deep liquid fuels, because the amount of emulsifier agent needed for extinguishment is a function of the volume of the fuel, whereas other agents such as aqueous film-forming foam need cover only the surface of the fuel to achieve vapor mitigation. Emulsions are used to manufacture polymer dispersions – polymer production in an emulsion 'phase' has
1020-432: Is also 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 detect high-energy elementary particles . A fluid system in which liquid droplets are dispersed in a liquid. Note 1 : The definition
1080-402: Is an attractive force between the droplets, so they form flocs, like bunches of grapes. This process can be desired, if controlled in its extent, to tune physical properties of emulsions such as their flow behaviour. Coalescence occurs when droplets bump into each other and combine to form a larger droplet, so the average droplet size increases over time. Emulsions can also undergo creaming, where
1140-411: Is based on the definition in ref. Note 2 : The droplets may be amorphous, liquid-crystalline, or any mixture thereof. Note 3 : The diameters of the droplets constituting the dispersed phase usually range from approximately 10 nm to 100 μm; i.e., the droplets may exceed the usual size limits for colloidal particles. Note 4 : An emulsion is termed an oil/water (o/w) emulsion if
1200-430: Is between 30 and 45 °C depending on the molecular weight. PVAc dispersions such as Elmer's Glue-All contain polyvinyl alcohol as a protective colloid . In alkaline conditions, boron compounds such as boric acid or borax cause the polyvinyl alcohol to cross-link , forming tackifying precipitates or toys, such as Slime and Flubber . A number of microorganisms can degrade polyvinyl acetate. Most commonly, damage
1260-544: Is called the " Tyndall effect ". If the emulsion is concentrated enough, the color will be distorted toward comparatively longer wavelengths, and will appear more yellow . This phenomenon is easily observable when comparing skimmed milk , which contains little fat, to cream , which contains a much higher concentration of milk fat. One example would be a mixture of water and oil. Two special classes of emulsions – microemulsions and nanoemulsions, with droplet sizes below 100 nm – appear translucent. This property
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#17328514532791320-507: Is caused by filamentous fungi ; however, algae , yeasts , lichens , and bacteria can also degrade polyvinyl acetate. Polyvinyl acetate was discovered in Germany in 1912 by Fritz Klatte . The monomer, vinyl acetate , was first produced on an industrial scale by the addition of acetic acid to acetylene with a mercury(I) salt, but it is now primarily made by palladium -catalyzed oxidative addition of acetic acid to ethylene . PVA
1380-446: Is commonly practiced by these individuals after discovering their intolerance or allergy. Casein that is heat-treated has been shown to be more allergenic and harder to digest when fed to infants. Breast milk has not typically been shown to cause an allergic reaction, but should be administered to an infant with caution each time in case of adverse reaction from something the breastfeeding parent consumed that contained casein. Following
1440-471: Is considered a food-safe material, and is thus used often in such applications (e.g., in food packaging material). Uses: The stiff homopolymer PVAc, but mostly the softer copolymer , a combination of vinyl acetate and ethylene, vinyl acetate ethylene (VAE), is also used in paper coatings, paint and other industrial coatings, as a binder in nonwovens in glass fibers , sanitary napkins , filter paper and in textile finishing . Polyvinyl acetate
1500-444: Is considered to be the most efficient protease for the cheese-making industry (Rao et al., 1998). British terminology, on the other hand, uses the term caseinogen for the uncoagulated protein and casein for the coagulated protein . As it exists in milk, it is a salt of calcium . An attractive property of the casein molecule is its ability to form a gel or clot in the stomach, which makes it very efficient in nutrient supply. The clot
1560-746: Is continuous depends in many cases on the pharmaceutical formulation . These emulsions may be called creams , ointments , liniments (balms), pastes , films , or liquids , depending mostly on their oil-to-water ratios, other additives, and their intended route of administration . The first 5 are topical dosage forms , and may be used on the surface of the skin , transdermally , ophthalmically , rectally , or vaginally . A highly liquid emulsion may also be used orally , or may be injected in some cases. Microemulsions are used to deliver vaccines and kill microbes . Typical emulsions used in these techniques are nanoemulsions of soybean oil , with particles that are 400–600 nm in diameter. The process
1620-664: 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 below about 100 nm, the light can penetrate through the emulsion without being scattered. Due to their similarity in appearance, translucent nanoemulsions and microemulsions are frequently confused. Unlike translucent nanoemulsions, which require specialized equipment to be produced, microemulsions are spontaneously formed by "solubilizing" oil molecules with
1680-420: Is exploited in soap , to remove grease for the purpose of cleaning . Many different emulsifiers are used in pharmacy to prepare emulsions such as creams and lotions . Common examples include emulsifying wax , polysorbate 20 , and ceteareth 20 . Sometimes the inner phase itself can act as an emulsifier, and the result is a nanoemulsion, where the inner state disperses into " nano-size " droplets within
1740-425: Is for the disinfection of surfaces. Some types of nanoemulsions have been shown to effectively destroy HIV-1 and tuberculosis pathogens on non- porous surfaces. Emulsifying agents are effective at extinguishing fires on small, thin-layer spills of flammable liquids ( class B fires ). Such agents encapsulate the fuel in a fuel-water emulsion, thereby trapping the flammable vapors in the water phase. This emulsion
1800-411: Is not 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 bacteria or viruses , they force
1860-479: Is not coagulated by heat. During the process of clotting, milk-clotting proteases act on the soluble portion of the caseins, κ-casein , thus originating an unstable micellar state that results in clot formation. When coagulated with chymosin , casein is sometimes called paracasein . Chymosin (EC 3.4.23.4) is an aspartic protease that specifically hydrolyzes the peptide bond in Phe105-Met106 of κ-casein, and
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1920-410: Is readily dispersible in dilute alkalis and in salt solutions such as aqueous sodium oxalate and sodium acetate . The enzyme trypsin can hydrolyze a phosphate -containing peptone . It is used to form a type of organic adhesive . Casein paint is a fast-drying, water-soluble medium used by artists. Casein paint has been used since ancient Egyptian times as a form of tempera paint, and
1980-416: Is relatively hydrophobic , making it poorly soluble in water . It is found in milk as a suspension of particles, called casein micelles , which show only limited resemblance with surfactant -type micelles in a sense that the hydrophilic parts reside at the surface and they are spherical. However, in sharp contrast to surfactant micelles, the interior of a casein micelle is highly hydrated. The caseins in
2040-661: Is the most common type found in cow's milk in Europe (excluding Italy and France which have more A2 cows), the United States, Australia, and New Zealand. Interest in the distinction between A1 and A2 beta-casein proteins began in the early 1990s through epidemiological research and animal studies initially conducted by scientists in New Zealand, which found correlations between the prevalence of milk with A1 beta-casein proteins and various chronic diseases. The research generated interest in
2100-432: The dispersed phase 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 inverse emulsion. The term "inverse emulsion" is misleading, suggesting incorrectly that the emulsion has properties that are
2160-569: The de Havilland Albatross airliner in 1939. Casein glue is also used in transformer manufacturing (specifically transformer board) due to its oil permeability. Elmer's Glue-All, Elmer's School Glue and many other Borden adhesives were originally made from casein. While one reason was its non-toxic nature, a primary factor was that it was economical to use. Towards the end of the 20th century, Borden replaced casein in all of its popular adhesives with synthetics like PVA . While largely replaced with synthetic resins, casein-based glues still have
2220-697: The A1 protein. A small fraction of the population is allergic to casein. Casein intolerance , also known as "milk protein intolerance", is experienced when the body cannot break down the proteins of casein. The prevalence of casein allergy or intolerance ranges from 0.25 to 4.9% of young children. Numbers for older children and adults are not known. A significant portion of those on the autism spectrum have an intolerance or allergy to casein protein into adulthood. This can be used by clinicians and dietitians to spot autism in those who may not present with traditional autistic traits . A diet known as casein-free, gluten free (CFGF)
2280-617: The US, is a widely available adhesive used for porous materials like wood, paper, and cloth. An aliphatic rubbery synthetic polymer with the formula (C 4 H 6 O 2 ) n , it belongs to the polyvinyl ester family, with the general formula −[RCOOCHCH 2 ]−. It is a type of thermoplastic . The degree of polymerization of polyvinyl acetate is typically 100 to 5000, while its ester groups are sensitive to base hydrolysis and slowly convert PVAc into polyvinyl alcohol and acetic acid . The glass transition temperature of polyvinyl acetate
2340-547: The beta-casein milk protein that differ by one amino acid ; a proline occurs at position 67 in the chain of amino acids that make up the A2 beta-casein, while in A1 beta-casein a histidine occurs at that position. Due to the way that beta-casein interacts with enzymes found in the digestive system, A1 and A2 are processed differently by digestive enzymes , and a seven-amino peptide , beta- casomorphin -7, (BCM-7) can be released by digestion of A1-beta-casein. The A1 beta-casein type
2400-399: The boundary between the phases called the "interface". Emulsions tend to have a cloudy appearance because the many phase interfaces scatter light as it passes through the emulsion. Emulsions appear white when all light is scattered equally. If the emulsion is dilute enough, higher-frequency (shorter-wavelength) light will be scattered more, and the emulsion will appear bluer – this
2460-501: The case of non-ionic surfactants or, on a broader scope, interactions between droplets within the system. Storing an emulsion at high temperatures enables the simulation of realistic conditions for a product (e.g., a tube of sunscreen emulsion in a car in the summer heat), but also accelerates destabilization processes up to 200 times. Mechanical methods of acceleration, including vibration, centrifugation, and agitation, can also be used. These methods are almost always empirical, without
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2520-416: The dispersed phase is denser than the continuous phase and the gravitational forces pull the denser globules towards the bottom of the emulsion. Similar to creaming, sedimentation follows Stokes' law . An appropriate surface active agent (or surfactant) can increase the kinetic stability of an emulsion so that the size of the droplets does not change significantly with time. The stability of an emulsion, like
2580-459: The droplets rise to the top of the emulsion under the influence of buoyancy , or under the influence of the centripetal force induced when a centrifuge is used. Creaming is a common phenomenon in dairy and non-dairy beverages (i.e. milk, coffee milk, almond milk , soy milk) and usually does not change the droplet size. Sedimentation is the opposite phenomenon of creaming and normally observed in water-in-oil emulsions. Sedimentation happens when
2640-400: The emulsion. An example 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. Whether an emulsion of oil and water turns into
2700-448: The evidence that such diets have any impact on behavior or cognitive and social functioning in autistic children was limited and weak. Casein proteins have potential for use as nanomaterials due to their readily available source (milk) and their propensity to self-assemble into amyloid fibrils. There is not enough good evidence that caseins in milk increase the risk of getting cancer . A1 and A2 beta-casein are genetic variants of
2760-482: The fat, then the milk is soured so that the casein is precipitated as milk curd . The curd is washed (removing the whey ), and then the curd is pressed to squeeze out the water (it may even be dried to a powder). The casein is mixed with alkali (usually both sodium and calcium hydroxide) to make glue. Glues made with different mixes of alkalis have different properties. Preservatives may also be added. They were popular for woodworking, including for aircraft, as late as
2820-399: The formulator must accelerate this process in order to test products in a reasonable time during product design. Thermal methods are the most commonly used – these consist of increasing the emulsion temperature to accelerate destabilization (if below critical temperatures for phase inversion or chemical degradation). Temperature affects not only the viscosity but also the interfacial tension in
2880-516: 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 not harm normal human cells, or the cells of most other higher 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 most effective application of this type of nanoemulsion
2940-419: The marketing of A2 milk, and the scientific evidence that had been published, an independent review published in 2005 found no discernible difference between drinking A1 or A2 milk on the risk of contracting chronic diseases. The European Food Safety Authority (EFSA) reviewed the scientific literature and published a review in 2009 found no identifiable relationship between chronic diseases and drinking milk with
3000-506: The media, among some in the scientific community, and entrepreneurs. A company, A2 Corporation, was founded in New Zealand in the early 2000s to commercialize the test and market "A2 Milk" as premium milk that is healthier due to the lack of peptides from A1. A2 Milk even petitioned the Food Standards Australia New Zealand regulatory authority to require a health warning on ordinary milk. Responding to public interest,
3060-402: The micelles are held together by calcium ions and hydrophobic interactions. Any of several molecular models could account for the special conformation of casein in the micelles. One of them proposes the micellar nucleus is formed by several submicelles, the periphery consisting of microvillosities of κ-casein. Another model suggests the nucleus is formed by casein-interlinked fibrils. Finally,
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#17328514532793120-570: The milk of cows , buffalo , goats , or sheep . It is produced by coagulation that is caused by destabilization of the casein micelle, which begins the processes of fractionation and selective concentration. Typically, the milk is acidified and then coagulated by the addition of rennet , containing a proteolytic enzyme known as rennin ; traditionally obtained from the stomachs of calves , but currently produced more often from genetically modified microorganisms. The solids are then separated and pressed into final form. Unlike many proteins, casein
3180-423: The most recent model proposes a double link among the caseins for gelling to take place. All three models consider micelles as colloidal particles formed by casein aggregates wrapped up in soluble κ-casein molecules. The isoelectric point of casein is 4.6. Since milk's pH is 6.6, casein has a negative charge in milk. The purified protein is water-insoluble. While it is also insoluble in neutral salt solutions, it
3240-461: The opposite of those of an emulsion. Its use is, therefore, not recommended. 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 ). Emulsions contain both a dispersed and a continuous phase, with
3300-478: The outer phase. A well-known example of this phenomenon, the " ouzo effect ", happens when water is poured into a strong alcoholic anise -based beverage, such as ouzo , pastis , absinthe , arak , or raki . The anisolic compounds, which are soluble in ethanol , then form nano-size droplets and emulsify within the water. The resulting color of the drink is opaque and milky white. A number of different chemical and physical processes and mechanisms can be involved in
3360-485: The process of emulsification: Oil-in-water emulsions are common in food products: Water-in-oil emulsions are less common in food, but still exist: 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 true emulsions. In pharmaceutics , hairstyling , personal hygiene , and cosmetics , emulsions are frequently used. These are usually oil and water emulsions but dispersed, and which
3420-418: The stability of a microemulsion is often easily compromised by dilution, by heating, or by changing pH levels. Common emulsions are inherently unstable and, thus, do not tend to form spontaneously. Energy input – through shaking, stirring, homogenizing , or exposure to power ultrasound – is needed to form an emulsion. Over time, emulsions tend to revert to the stable state of the phases comprising
3480-443: The type of emulsifier greatly affects how emulsions are structured in the stomach and how accessible the oil is for gastric lipases , thereby influencing how fast emulsions are digested and trigger a satiety inducing hormone response. Detergents are another class of surfactant, and will interact physically with both oil and water , thus stabilizing the interface between the oil and water droplets in suspension. This principle
3540-692: Was well known for use in buttons . Fiber can be made from extruded casein. Lanital , a fabric made from casein fiber (known as Aralac in the United States), was particularly popular in Italy during the 1930s. Casein-derived compounds are used in tooth remineralization products to stabilize amorphous calcium phosphate (ACP) and release the ACP onto tooth surfaces, where it can facilitate remineralization. Casein and gluten exclusion diets are sometimes used in alternative medicine for children with autism . As of 2015
3600-416: Was widely used by commercial illustrators as the material of choice until the late 1960s when, with the advent of acrylic paint , casein became less popular. It is still widely used by scenic painters, although acrylic has made inroads in that field as well. Casein-based glues are formulated from casein, water, and alkalis (usually a mix of hydrated lime and sodium hydroxide ). Milk is skimmed to remove
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