Casein applications

In a totally different area of application, casein adhesives for paper sizing, chipboard laminating, and label gluing are more nearly casein solutions [59,60]. They are simple dispersions with ammonia or borax at moderate pH and low viscosity. They are frequently combined with latexes or soluble rosin derivatives for special performance improvements [59]. 

As well as being central to cheesemaking, casein is used to fortify flour, bread and cereals. In addition to its functions in food products, casein has many other industrial applications. Casein is much used in tonics and dietary supplements (Section 12.13). Caseinates are surfactants and will act as emulsifiers, water and fat binders, adhesives, thickening and gelling agents (Section 12.4). Either additional phosphorylation or dephosphorylation of casein can be carried out with consequent modification of some of its properties. 

Although acid caseins are employed for a number of purposes, rennet caseins in which the protein remains associated with calcium and phosphate are preferred for plastics applications. Rennet is the dried extract of rennin, obtained from the inner lining of the fourth stomach of calves, and is a very powerful coagulant. As little as 0.2 parts per million are said to be sufficient to coagulate slightly acidic milk. Its coagulating power is destroyed at 100°C. 

Formolised casein is a rigid hom-like material which may be made available in a wide variety of colours and patterns. By common consent it is recognised as having a pleasant feel and appearance and it is properties which are relevant to cuiTent commercial application. 

When dry, casein is a good electrical insulator but is seriously affected by humid conditions. For this reason it can no longer compete with the many alternative plastics materials now available for electrical applications. 

In the past casein plastics were widely used for decorative applications where a pleasant appearance was of value. The button industry was by far the largest user with further use for buckles, slides, hair pins, knitting pins, pens and pencils. 

Chemical nature Isolation of casein from milk Production of casein plastics Properties of casein Applications Miscellaneous Protein Plastics Derivatives of Natural Rubber Gutta Percha and Related Materials Shellac... 

Many proteins and polymers have been analyzed on SynChropak GPC and CATSEC columns. Table 10.6 lists some of the published applications. The use of a surfactant to analyze the caseins in milk is illustrated in Eig. 10.12. Viruses have also been analyzed on SynChropak GPC columns, as seen in the chromatogram from Dr. Jerson Silva of the University of Illinois (Pig. 10.13). Dr. Nagy and Mr. Terwilliger analyzed cationic polymers on a series of CATSEC columns using differential viscometry as detection (Pig. 10.14) (9). 

Developments in glued laminated structures and panel products such as plywood and chipboard raises the question of the durability of adhesives as well as wood. Urea-formaldehyde adhesives are most commonly used for indoor components. For exterior use, resorcinol adhesives are used for assembly work, whilst phenolic, tannin and melamine/urea adhesives are used for manufactured wood products. Urea and casein adhesives can give good outdoor service if protected with well-maintained surface finishes. Assembly failures of adhesives caused by exudates from some timber species can be avoided by freshly sanding the surfaces before glue application. 

The utilization of the vegetable gums, especially those with good filmforming properties, to suspend the solids in paints of the casein and emulsion types, still offers a wide field for experimentation and application. 

Farrell, H. M., Jr., Qi, P. X., and Uversky, V. N. (2006a). New views of protein structure Applications to the caseins. In "Advances in Biopolymers Molecules, Clusters, Networks and Interactions", pp. 52-70. American Chemical Society, Washington, DC. 

Besides the previously mentioned collagen, a wide variety of natural polymers have been involved in the synthesis of bio-nanohybrid materials with potential application in bone repair and dental prostheses. For instance, some recent examples refer to bionanocomposites based on the combination of HAP with alginate [96,97], chitosan [98,99], bovine serum albumin (BSA) [100], sodium caseinate [101], hyaluronic acid [102], silk fibroin [103,104], silk sericin [105], or polylactic add (PLA) [106,107]. These examples illustrate the increasing interest in the subject of HAP-based biohybrid materials, which has led to almost 400 articles appeared in scientific journals in 2006 alone. 

P-Casein, synthesis, 151,153/ Caseinomacropeptide, laige-scale preparation and application, 211-219 amino acid composition, 219t biological functions, 211 inhibition of cholera toxin-receptor binding, 211-214 isolation procedure, 215,217/218 molecular weights, 215,216/ potential applications, 219 preparation, 215-219 recovery, 218/,219r... 

Two main types of analysis are required (a) qualitative determination of the presence of elements and (b) quantitative determination of the amount of elements or species of interest contained in pharmaceutical products. Most analyses for pharmaceutical applications involve separation steps combined with ICP-MS, such as HPLC-ICP-MS or gel electrophoresis and the analysis of gel blots by LA-ICP-MS. Phosphorylated proteins (e.g., (3-casein) have been measured by LA-ICP-MS with a detection limit of 16pmol. HPLC-ICP-MS has been employed for the identification and quantification of metabolites of bradykinin in human and rat plasma.1... 

Quinn and Paton (16) observed that the intensity and duration of mixing influenced the water uptake of the materials investigated, and that the measurement was not reproducible unless the time of agitation was constant (2 min was chosen). One product, sodium caseinate, required longer than a 2-min mixing time. These investigators state that the proposed technique measures water absorbed and retained under specific conditions, which may or may not apply to particular manufacturing applications. They do, however, state that this method with the application of limited... 

Milk protein products. As indicated in Table 1, the food industry is placing major emphasis on the production and utilization of milk protein products in a wide variety of formulated food products (20,21,22). Although nonfat dry milk (NFDM) and whey powder are major milk protein ingredients in formulated foods, casein and whey protein concentrates, which contain their proteins in a more highly concentrated and functional form, are essential for certain food product applications, such as those products that require the proteins as an emulsifier agent. Additional details on the processing methods and conditions used to produce the various milk protein products are available (23). 

NFDM, which retains casein micelles similar to those in fresh milk, is produced by pasteurization of sklmmllk, vacuum concentration and spray drying under processing conditions that result in either "low heat" or "high heat" product. Low heat NFDM is required for most applications that depend upon a highly soluble protein, as the case for most emulsification applications, since it is manufactured under mild temperature conditions to minimize whey protein denaturation and complexation with casein micelles. 

Co-preclpltate is an insoluble milk protein product that is produced by heating skinimllk to high temperatures ( > 90 C) to denature the whey proteins and complex them with the casein micelles. The heated system is subsequently adjusted to isoelectric point conditions of pH 4.5-5 to precipitate the complexed whey protein-casein micelles, centrifuged or filtered to recover the precipitate, washed and dryed. The resulting product, which is virtually insoluble, exhibits only minor functionality in most typical emulsification applications. 

Emulsification properties. Caseins and caseinates are commonly selected for food product applications that require surfactant properties, e.g., emulsification and foam stabilization, since they contain high protein contents of > 90 %, are highly soluble, and are resistant to heat-induced denaturatlon in products to be subjected to high temperature processing conditions (15). 

Casein may be coagulated and recovered as rennet casein by treatment of milk with selected proteinases (rennets). However, one of the caseins, K-casein, is hydrolysed during renneting and therefore the properties of rennet casein differ fundamentally from those of acid casein. Rennet casein, which contains the colloidal calcium phosphate of milk, is insoluble in water at pH 7 but can be dissolved by adding calcium sequestering agents, usually citrates or polyphosphates. It has desirable functional properties for certain food applications, e.g. in the production of cheese analogues. 

Principal micelle characteristics. The structure of the casein micelles has attracted the attention of scientists for a considerable time. Knowledge of micelle structure is important because the stability and behaviour of the micelles are central to many dairy processing operations, e.g. cheese manufacture, stability of sterilized, sweetened-condensed and reconstituted milks and frozen products. Without knowledge of the structure and properties of the casein micelle, attempts to solve many technological problems faced by the dairy industry will be empirical and not generally applicable. From the academic viewpoint, the casein micelle presents an interesting and complex problem in protein quaternary structure. 

Addeo, F., Chobert, J.-M. and Ribadeau-Dumas, B. 1977. Fractionation of whole casein on hydroxyapatite. Application of a study of buffalo kappa-casein. J. Dairy Res. 44, 63-68. 

Morr, C. V., Van Winkle, Q. and Gould, I. A. 1962. Application of polarization of fluorescence technique to protein studies. III. The interaction of x-casein and (3-lacto-globulin. J. Dairy Sci. 45, 823-826. 

---