Physical properties casein

Reclaimed mbber, which is widely used in dry mbber, has Htde use in latex compounding. A dispersion or artificial latex of the red aim must be made by a rather expensive process of milling in dispersing agents, eg, soaps and casein, and water. Some reclaim dispersions are used in latex compounds for such things as spread mbber goods and adhesives and fiber binders to reduce cost. However, for most latex compounds, it is not desirable because of the poor physical properties it imparts and the resultant darkening of the compound. 

Table 30.2 Some physical properties o casein plastics...

The precipitation of casein in its uncombincd form by the addition to milk of one or another acid, forms the basis of all methods of preparation. These differ widely, however, in the subsequent purification. In the method of Hammarsten,4 just enough alkali is added to dissolve this casein completely. The alkalinity reached in this process somewhat modifies its physical properties but probably not its composition. In the method of Van Slyke and Bosworth 5 the last trace of calcium is removed by adding oxalate to an ammoniacal solution of the casein, but... 

Mahmoud, M.I., Malone, W.T., and Cordle, C.T. 1992. Enzymatic hydrolysis of casein effect of degree of hydrolysis on antigenicity and physical properties. J. Food Sci. 57, 1223—1229. 

Table IX. Some Physical Properties of Casein Modified by Covalent Attachment of Some Amino Acids0...

Practical Coacervate Formation. The composition of the various parts of the coacervate system was determined by using l c-labelled kappa-casein as one component of the coacervates, and then performing a mass balance on the system. The C-kappa-casein was prepared by reductive methylation of kappa-casein with l C-formaldehyde (15), This derivatization of kappa-casein was found not to materially affect its physical properties (16). 

Longares, A., Monahan, F.J., O Riordan, E.D., and O Sullivan, M. (2005). Physical properties of edible films made from mixtures of sodium caseinate and WPl. Int. Dairy J. 15, 1255-1260. 

Different proteins have different physical properties. Some—such as casein in milk, ovalbumin in egg whites, and hemoglobin in blood—are water-soluble. Others—such as keratin in hair, fibroin in spider silk, and collagen in connective tissue—are flexible solids. 

The alteration of mineral and casein equilibria is reflected in changes to the physical properties of milk. The addition of citrate and different types of phosphates (ortho-, pyro-, or hexameta) to milk protein concentrate solutions, which alters the distribution of calcium and inorganic phosphate between the colloidal and serum phases of milk, affects its turbidity and buffering capacity (Mizuno and Lucey, 2005). The turbidity is affected because dissolution of colloidal calcium phosphate is accompanied by release of caseins into the serum. 

Arvanitoyannis, i. and Biliaderis, C. Physical properties of polyol-plasticized edible films made from sodium caseinate and soluble starch blends. Food Chem., 62,... 

Some physical properties of casein plastics are given in Table 4. 

An additional example of how enzymes can affect the physical properties of purified proteins relates to the enzymic dephosphorylation of /3-casein (4). Bovine /3-casein contains five phosphate groups per monomer as phosphoseryl residues. Purified /3-casein from bovine milk was dephosphorylated by a phosphoprotein phosphatase. Both the native /3-casein and 65% dephosphorylated /3-casein self-associated to form polymers at 35°C. However, the dephosphorylated /3-casein had a larger sedimentation coefficient (S35 22.5) than that of the native /3-casein (S35 18.2). Also the sedimentation pattern of the dephosphorylated /3-casein was more polydisperse than the hypersharp pattern of the native /3-casein. These properties were accentuated with 95% dephosphorylated /3-casein. The decrease in the negative charge caused by the loss of phosphate apparently favors the self-association of /3-casein resulting from hydrophobic bonding. 

Milk contains 3.3% total protein. There are two major categories of milk protein that are broadly defined by their chemical composition and physical properties. The casein family contains phosphorus and will coagulate or precipitate at pH 4.6. The serum [whey] proteins do not contain phosphorus, and these proteins remain in solution in milk at pH 4.6. The principle of coagulation, or curd formation, at reduced pH is the basis for cheese curd formation. In cow s milk, approximately 82% of milk protein is casein and the remaining 18% is serum, or whey protein. 

Dangaran, K.L., Cooke, P., Tomasula, P.M. The effect of protein particle size reduction on the physical properties of C02-precipitated casein films. J. Food Sci. 71, 196—201 (2006)... 

Casein has been found to be an excellent candidate to produce oil-in-water emulsions that have both high physical and oxidative stability. The differences in the physical properties and oxidative stability of com oil-in-water emulsions stabilized by casein, WPI, or SPI at pH 3.0, have been investigated. Emulsions have been prepared with 5 per cent com oil and 0.2-1.5 per cent protein. Physically stable, monomodal emulsions have been prepared with 1.5 per cent casein, 1.0 or 1.5 per cent SPI, and 2=0.5 per cent WPI. The oxidation stability of the different protein-stabilized emulsions was in the order of casein > WPI > SPI, as determined by monitoring both lipid hydroperoxide and headspace hexanal formation. The degree of positive charge on the protein-stabilized emulsion droplets was not the only factor involved in the inhibition of lipid oxidation, because the charge of the emulsion droplets... 

There is some variation in the average composition of milk taken from different animal species, but the same major classes of compound are always present (Table 12.11). Average physical properties are indicated in Table 12.12. Milk phosphoproteins are mostly present in the caseins but also to a smaller extent in the numerous enzymes (e.g. phosphatases, lipases, ribonucleases). 

Casein and caseinate are utilized as food and also have nonfood uses. In food manufacturing they are used for protein enrichment and/or to achieve stabilization of some physical properties of processed meats, baked products, candies, cereal products, ice creams, whipping creams, coffee whiteners, and some dietetic food products and drugs. 

About 50 years ago, the major uses of casein were in technogical appUcations, but nowadays casein products are regularly used as food additives, for example as ingredients that enhance some physical properties of foods, such as whipping, foaming, water binding, thickening and emulsification and nutritional properties. 

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