Casein micelles properties

A useful property of the red seaweed extracts is their abiUty to form gels with water and milk. Kappa-carrageenan reacts with milk protein micelles, particularly kappa-casein micelles. The thickening effect of kappa-carrageenan in milk is 5—10 times greater than it is in water at a concentration of 0.025% in milk, a weak thixotropic gel is formed. 

Caseins are the major proteins in bovine milk and about 95% of the caseins exist as casein micelles. The structure and properties of casein micelles influence a wide range of technological uses of milk. Light microscopy, SEM, and TEM have been frequently used to study casein... 

The essence of the shell model is that the association constant of the first step is very much smaller than the association constants of all subsequent steps. It was assumed by de Kruif et al. (2002) that, since there is a considerable similarity in various properties of p- and K-caseins, then the k-casein micelle can also be described using the shell model. Nevertheless, Vreeman et al. (1981) had previously suggested that the structure of the... 

Creamer, L.K., Berry, G.P. (1975). A study of the properties of dissociated bovine casein micelles. Journal of Dairy Research, 42, 169-183. 

McGann, T.C.A., Fox, P.F. (1974). Physico-chemical properties of casein micelles reformed front urea-treated milk. Journal of Dairy Research, 41, 45-53. 

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. 

Since the pioneering work of Waugh in 1958, a considerable amount of research effort has been devoted to elucidating the structure of the casein micelle, and several models have been proposed. This work has been reviewed in the references cited in the next section. The principal properties of the casein micelles are listed below and the models which best meet these requirements discussed briefly in the next section. 

Although CCP represents only about 6% of the dry weight of the casein micelle, it plays an essential role in its structure and properties and hence has major effects on the properties of milk it is the integrating factor in the casein micelle without it, milk is not coagulable by rennet and its heat and calcium stability properties are significantly altered. In fact, milk would be a totally different fluid without colloidal calcium phosphate. 

Although the gelation properties of whey proteins are of great importance in many foods (Mulvihill, 1992) and it is possible to form a weak gel in creams by the formation of a continuous network of fat globules, most important milk gels are those involving casein micelles which can be made to form a gel matrix either by isoelectric precipitation (acid-induced gel) or by the action of a proteolytic enzyme (rennet-induced gel). Both gel types... 

Hegenauer, J., Saltman, P., Ludwig, D., Ripley, L. and Ley, A. 1979. Iron-supplemented cow milk. Identification and spectral properties of iron bound to casein micelles. J. Agr. Food Chem. 27, 1294-1301. 

The ageing at 5°C of whippable emulsions such as ice cream mix will enhance the hydration of milk proteins in the system. This is due to a property of casein micelles in milk. At low temperatures, the hydration or voluminosity of casein increases. The voluminosity is the volume of hydrated protein per gram of protein. This can be studied by analyzing the protein and water content in the sedimented casein pellet after centrifugation of skimmed milk. 

According to Bloomfield and Mead (1974), The ultimate goal of all workers on casein is to reconstitute micelles with native properties from the separated constituents of skim-milk. This assertion reflects the large number of studies in the literature on the precipitation and association properties of the caseins.There are, however, legitimate scientific goals in this kind of work other than the creation of artificial casein micelles, such as the elucidation of the mechanisms by which phosphoproteins profoundly influence the nucleation and growth of calcium phosphate phases. 

The most thorough study of the formation of artificial casein micelles is that of Schmidt and co-workers (1977 1979 Schmidt and Koops, 1977 Schmidt and Both, 1982 Schmidt and Poll, 1989), who not only studied the properties of the casein aggregates but also attempted to relate them to the solution conditions under which they were formed. In the precipitation of calcium phosphate from solution, the means by which solutions are mixed together is of crucial importance Schmidt et al. (1977) described a method in which four solutions were pumped simultaneously into a reaction vessel while keeping the pH constant. As a result of careful, slow mixing, the reproducibility of the size distributions of particles, measured by electron microscopy on freeze-fractured and freeze-etched specimens, was very good. In the first series of experiments, the objective was to produce milk like concentrations of the most important ions while... 

Dalgleish, D. G., and Morris, E. R. (1988). Interactions between carrageenans and casein micelles electrophoretic and hydrodynamic properties of the particles. Food Hydrocoll. 4 311-320. 

Yoshikawa, M., Sasakai, R., and Chiba, H. 1981. Effect of chemical phosphorylation of bovine casein components on the properties related to casein micelle formation. Agric. Biol. Chem. 45,... 

This paper draws heavily upon the "Nomenclature Committee Report" ( 1) as well as several recent comprehensive reports that have considered the primary structure and conformation of the casein monomer subunits and how they are assembled into submicel-lar aggregates and casein micelles (2, 3). These basic relationships were utilized to develop additional projections relating to the conformation and functional properties of the major milk proteins, e.g., commercial caseinates and whey protein concentrates in food applications. 

K-casein also contains two Cys residues per monomer subunit and is thus capable of interacting with the whey proteins, e.g., mainly g-lactoglobulin, via the disulfide interchange mechanism at temperatures at or above 65°C. This latter phenomenon is believed to be important in providing colloidal stability to the milk casein micelle system, as well as to the whey proteins, in high temperature processed milk products. It has also been postulated that this latter interaction with g-lactoglobulin may alter the availability of K-casein in the micelle, and thus has a detrimental effect upon the cheese making properties of milk (4). 

The major caseins exist in milk as highly structured, spherical aggregates, consisting of 450 to 10,000 subunits (3), commonly referred to as micelles. The important physico-chemical properties of the micelles are summarized in Table 3. Casein micelles are synthesized in vivo by biochemically controlled processes., which have not been totally characterized (5). Even... 

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