Protective colloid, casein

In the manufacture of articles direct from latex it is necessary to stabilise the latex (to prevent premature coagulation) by the addition of protective colloids such as casein soaps, gelatine and proprietary anionic surface active agents. 

Kreuter and Speiser [77] developed a dispersion polymerization producing adjuvant nanospheres of polymethylmethacrylate) (PMMA). The monomer is dissolved in phosphate buffered saline and initiated by gamma radiation in the presence and absence of influenza virions. These systems showed enhanced adjuvant effect over aluminum hydroxide and prolonged antibody response. PMMA particles could be distinguished by TEM studies and the particle size was reported elsewhere to be 130 nm by photon correlation spectroscopy [75], The particle size could be reduced, producing monodisperse particles by inclusion of protective colloids, such as proteins or casein [40], Poly(methylmethacrylate) nanoparticles are also prepared... 

In addition to the above, there are emulsion and suspension stabilizers that act as protective colloids and in some cases as thickeners gums (such as acacia and traga canth), alginates, starch and starch derivatives, casein, glue, egg albumin, methyl cellulose, hydrated Mg and Al silicates, etc Refs Same as in previous item... 

The reaction of starch phosphate with such proteins as soybean protein and casein was used to produce protective colloids for insolubilization of pigments in coatings and paper.1684 The complexation of starch phosphate with protein insolubilizes the latter, particularly when starch phosphate is in the form of an ammonium salt.1685... 

Premature flocculation can be an interference. Sodium silicate is used as a dispersant. Starch, casein, and glue are used to disperse both gangue and carbonaceous matter. They also serve as protective colloids to prevent reflocculation, such as in the flotation of gold. 

Definition Hydrolysate of casein derived by acid, enzyme, or other method of hydrolysis Toxicology TSCA listed Uses Antistat, skin conditioner, hair conditioner, emollient, protective colloid, chelating agent in cosmetics stabilizer for colloids and emulsions binder, emulsifier, film-former in foods, pharmaceuticals, personal care prods., nutritional prods. Features Substantive to hair and skin Manuf/Distiib. Adept Sol ns. Alfa Chem http //WWW.alfachem.homepage, com] Am. 

Casein is the most important protein body in milk. Besides its chief function as nitrogenous food it plays the important role of protective colloid for the fat particles and also for calcium phosphate with which it forms a colloidal combination. It keeps the fat particles in a fine state of emulsion and prevents them from uniting into clots, probably due to the formation of a fine membrane around the particle. Casein may be precipitated from milk by acids. It is insoluble in water and also in the solutions of neutral salts, except sodium fluoride and potassium oxalate. Casein has acid properties, drives carbon dioxide out of carbonates, and is soluble in alkalis. The ammoniacal solution possesses a high protective effect toward colloidal gold. The gold number 0.01 indicates that it belongs therefore to the protective colloids of the first class. The behavior toward bases has been care-... 

If it is necessary to prevent the precipitation or coagulation of casein by acids a protective colloid stable against acids must be added, such as gelatin, or albumin. According to J. Alexander these additions are necessary in the preparation of ice cream. If the protective colloid... 

The albumin acts as a protective colloid for the casein and this explains the different behavior of the two substances. Several American medical men have realized this difference and favor the addition of protective colloids such as gum arabic, dextrin, etc., to cow s milk before giving it to children. Alexander has shown that cow s milk may be made to react much more like human milk if the protective colloids are added. Some authors have also claimed that casein from the two sources is not the same. This is probably due to the protective action of the albumin, because by dissolving the casein from human milk, and reprecipitating several times, it resembles more and more that from cow s milk. 

Coagulation of Fat Particles. — The casein and the albumin act as protective colloids for the fat particles, hence it is necessary to offset this protective effect before the fat or butter can be obtained free from the casein. It is generally believed that the casein forms an envelope around the fat particles, but other explanations of protective action have been offered, f... 

The fat may be separated quickly from the liquids if acid is added. Small amounts of sulfuric acid precipitate the casein, and the fat now being unprotected comes out with the casein. On the other hand if concentrated sulfuric acid is added the casein is dissolved, owing to its Wiegner, Kolloidzeit, 15, 105 (1914). t Theories of Protective Colloids, page 111. 

Casein is utilized in diverse ways, as an adhesive, as a binder, and as a protective colloid and stabilizer for emulsified adhesive systems. Casein is sold as a raw material, and casein adhesives are sold in both the dry and liquid forms. The useful wood adhesive known as casein glue, which is formulated with lime and sodium salts, will be addressed later. This section will cover other uses of casein, for which the solubilization of the casein is generally accomplished with the use of heat, and at lower pH s than for the lime-containing glues. 

Some of the information on the use of casein as a protective colloid was obtained as a personal communication from colleagues, who requested no credit be given. 

Dyestuffs and pigment dispersions need dispersing agents (sulfonated oils and esters, fatty acid condensation products and ethoxylates). They are used in combination with protective colloids [cellulose derivatives, alginates (- sodium alginate), - casein and - lignosulfonate]. 

All hydrophilic colloids possess some degree of protective action and gelatin, starch and casein are used commercially for this purpose. 

Kermack and Wright Biochem. J. XVII. 635,1923) have shown that gelatine at a of 4 T exerts but little protective power on a negative gum benzoin sol, acid gelatine precipitates the colloid in small concentrations whilst alkaline gelatine protects it. Similar observations have been made by Zsigmondy on the effect of casein on gold, but its exact isoelectric point was not established. 

Association with casein. The colloidal calcium phosphate is closely associated with the casein it does not precipitate out of solution and is considered to be protected against precipitation by the casein. Two possible forms of protection are suggested ... 

As with other viscous polyanions such as carrageenan, pectin may be protective towards milk casein colloids, enhancing the properties (foam stability, solubility, gelation and emulsification) of whey proteins whilst utilizing them as a source of calcium. 

Milk is a natural colloidal dispersion that contains casein micelles, self-assembled protein associates with a diameter of about 200 nm [20]. The casein micelles are protected against flocculation by an assembly of dense hairs (often called a brush ) at their surfaces. Polymer brushes can thus provide steric stabilization of colloids. For millennia, man used the fact that milk flocculates and gels when it is acidified, as in yogurt production. Below pH = 5 macroscopic flocculation of the casein micelles in milk is observed [21]. This means that the interactions between casein micelles change from repulsive to attractive. The explanation is that acidification leads to collapse of the casein brushes [22]. In cheese-making the steric stabilization is removed by enzymes, which induce gelation into cheese curd. 

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