Casein structure

Casein is a protein that is found in milk and is used independently in many foods as a binding agent. Its structure comprises the presence of amino acids. Amino acids have a variety of chemically reactive groups like phenolic hydroxy groups, presence of peptide bonds. Casein also includes amino groups, ketones and hydrazine groups. Its structure is shown in Fig. 5.5. 

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Home, D.S. (2002). Casein structure, self-assembly and gelation. Current Opinion in Colloid and Interface Science, 7, 456 461. 

Foumet, B., Fiat, A.-M., Alais, C. and Jolliis, P. 1979. Cow K-casein Structure of carbohydrate portion. Biochim. Biophys. Acta 576, 339-346. 

Jolles, J., Schoentgen, F Alais, C., Fiat, A.-M. and Joll6s, P 1972A. Studies on the primary structure of cow K-casein. Structural features of para-K-casein N-terminal sequence of K-casein-glycopeptides studied with a sequencer. Helv. Chim. Acta 55, 2872-2883. 

Temperature control is important in conductivity measurements, since the conductivity of milk increases by about 0.0001 ohm 1cm 1 per degree Celsius rise in temperature (Gerber 1927 Muller 1931 Pinkerton and Peters 1958). Increased dissociation of the electrolytes and decreasing viscosity of the medium with increasing temperature are undoubtedly responsible for this effect. An investigation (Sudheendra-nath and Rao 1970) of the viscosity and electrical conductivity of skim milk from cows and buffaloes failed to reveal a simple relationship. The authors attributed the lack of linear correlations to variations in casein structure and its hydration. 

Farrell, H.M. Jr., Wickham, E.D., Unmh, J.J., Qi, P.X., and Hoagland, P.D. 2001. Secondary structural studies of bovine caseins Temperature dependence of J-casein structure as analyzed by circular dichroism and FTIR spectroscopy and correlation with micellization. Food Hydrocolloids 15 341-354. 

Cheese, for example, has been demonstrated in clinical trials to have a smaller effect in raising LDL-cholesterol in comparison to butter and even milk (Tholstrup et al., 2004). Cheese is unique from other dairy products due to its physical structure, whereby its fat content is encapsulated within a casein structure (Fellows, 2000). 

Kumosinski, T.F., Brown, E.M. and Farrell, H.M. Jr (1993a) Three-dimensional molecular modeling of bovine caseins An energy-minimized /3-casein structure. J. Dairy Sci., 76, 931-45. 

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. 

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. 

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... 

FIGURE 6.10 Three characteristic structures of pressure-treated casein micelles representative AFM images together with the associated size-histograms are shown. The solid lines are fit to Gauss distributions. (A) Intact micelles, P < SO MPa (B) compact reconstituted micelles, 120 MPa < P < 240 MPa (C) mini-micelles, P > 280 MPa. Reprinted with permission from Gebhardt et al. (2006). 

Dalgleish, D. G., Spagnuolo, P. A., and Douglas Goff, H. (2004). A possible structure of the casein micelle based on high-resolution field emission scanning electron microscopy. Int. Dairy. 14,1025-1031. 

Farrell, H. M., Jr., Malin, E. L., Brown, E. M., and Qi, P. X. (2006). Casein micelle structure What can be learned from milk synthesis and structural biology Curr. Opin. Colloid Interface Sci. 11,135-147. 

Horne, D. S. (2009). Casein micelles structure and stability. In "Milk Proteins From Expression to Food", (A. Thompson, M. Boland, and H. Singh, Eds), pp. 133-179. Academic Press, San Diego. 

McMahon, D. J. and McManus, W. R. (1998). Rethinking casein micelle structure using electron microscopy. /. Dairy Sci. 81,2985-2993. 

The six major proteins of milk, asl-, o s2-, and /c-casein, jS-lactoglobulin, and a-lactalbumin, contain at least one tryptophan residue [57], the fluorescence of which allows the monitoring of the structural modifications of proteins and their physicochemical environment during the coagulation processes. Emission fluorescence spectra of the protein tryptophanyl residues were recorded for the milk coagulation kinetics induced by... 

It is generally not recommended to mix medications directly into the EN formula because of concerns that physical incompatibilities between the medications and the formula might lead to tube occlusion. There is some evidence that polymeric formulas are more likely to demonstrate physical incompatibility with medications compared with monomeric formulas, although most of the work in this area has used casein or caseinate-based formulas, and other proteins may act differently.38 The limited data currently available would indicate that acidic syrups and elixirs may be the worst for causing physical incompatibility when admixed with EN formulas. It has been postulated that this incompatibility is due to changes in the protein structure after exposure to acid or alcohol.38... 

These studies suggest that the caseins, synucleins, and tau have natively unfolded structures in which the sequences are based largely on the PPII conformation and are held together in a loose noncooperative fashion. However, rather than describing them as random coil ,... 

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