Casein adsorption

Dickinson, E., Horne, D.S., Pinfield, V.J., Leermakers, F.A.M. (1997). Self-consistent-field modelling of casein adsorption. Comparison of results for asi-casein and p-casein. Journal of the Chemical Society, Faraday Transactions, 93, 425 132. 

Sausse, R, Aguie-Beghin, V., Douillard, R. (2003). Effects of epigallocatechin gallate on beta-casein adsorption at the air/water inieTlace.Langmuir, 19, Ihl—lAh. 

The adsorption of proteins at fluid interfaces is a key step in the stabilization of numerous food and non-food foams and emulsions.1 Our general goal is to relate the amino acid sequence of proteins to their surface properties, e. g. to the equation of state or other structural and thermodynamic properties. To improve this understanding, the effect of guanidine hydrochloride (Gu HC1) on /1-casein adsorption is evaluated in the framework of the block-copolymer model for the adsorption of this protein. At first the main features of the model are presented, and then the effect of Gu HC1 is interpreted using the previously introduced concepts. 

Figure 6 Effect of the Gu HCl volume concentration on the relation between the dilational modulus and the surface pressure of casein adsorption layers formed from a 100 mg/L solution at 10°C. Gu HCl concentration ( + ), 0 A/ (U), 1 M (O), 2 M (O), 4M...

The carrier materials used for enzyme adsorption must have a highly porous character and a pore size distribution, which should facihtate a free diffusion of enzyme into the carrier. Furthermore, substrate and product should also be able to diffuse freely. This is especially important in the case of large protein substrates, where diffusion into the pore can be a problem (e.g. whey protein and casein). 

Experiments on interactions of polysaccharides with casein micelles show similar trends to those with casein-coated droplets. For example, Maroziene and de Kruif (2000) demonstrated the pH-reversible adsorption of pectin molecules onto casein micelles at pH = 5.3, with bridging flocculation of casein micelles observed at low polysaccharide concentrations. In turn, Tromp et al. (2004) have found that complexes of casein micelles with adsorbed high-methoxy pectin (DE = 72.2%) form a self-supporting network which can provide colloidal stability in acidified milk drinks. It was inferred that non-adsorbed pectin in the serum was linked to this network owing to the absence of mobility of all the pectin in the micellar casein dispersion. Hence it seems that the presence of non-adsorbed pectin is not needed to maintain stability of an acid milk drink system. It was stated by Tromp et al. (2004) that the adsorption of pectin was irreversible in practical terms, i.e., the polysaccharide did not desorb under the influence of thermal motion. 

Anand, K., Damodaran, S. (1996). Dynamics of exchange between asi-casein and p-casein during adsorption at air-water interface. Journal of Agricultural and Food Chemistry, 44, 1022-1028. 

Caessens, P.W.J.R., de Jongh, H.H.J., Norde, W., Gruppen, H. (1999). The adsorption-induced secondary structure of p-casein and of distinct parts of its sequence in relation to foam and emulsion properties. Biochimica et Biophysica Acta, 1430, 73-83. 

Cornec, M., Mackie, A.R., Wilde, P.J., Clark, D.C. (1996). Competitive adsorption of p-lactoglobulin and p-casein with Span 80 at the oil-water interface and the effect on emulsion behaviour. Colloids and Surfaces A Physicochemical and Engineering Aspects, 114, 237-244. 

Damodaran, S., Razumovsky, L. (2003). Competitive adsorption and thermodynamic incompatibility of mixing of p-casein and gum arabic at the air-water interface. Food Hydrocolloids, 17, 355-363. 

Dickinson, E., Horne, D.S., Phipps, J.S., Richardson, R.M. (1993a). A neutron reflectivity study of the adsorption of p-casein at fluid interfaces. Langmuir, 9, 242-248. 

The concentrated milk is homogenized at 140 to 210 kg/cm2 (2000 to 3000 lb/in2) at about 48°C (Hall and Hedrick 1966). This process is essential to provide adequate physical stability to the milk fat emulsion system to withstand prolonged storage at room temperature (Brunner 1974). However, homogenization lowers the heat stability of concentrated milk products (Parry 1974), which may be due to increased adsorption of casein micelles onto the newly created milk fat globule surfaces, thus making them more sensitive to heat-induced aggregation. 

Proteins that remain in whey after removing casein from milk are recovered as whey protein concentrates by precipitation with added polyphosphate or other polyvalent anionic compounds, ultrafiltration, ion exchange adsorption, gel filtration, or a combined acid and heat precipitation process. Whey protein concentrates are also manufactured by a combined process involving electrodialysis, concentration, lactose crystallization, and drying (Richert 1975 Morr 1979 Marshall 1982 Anon. 1982 Muller 1982B). 

Krisdhasima, V., Vinaraphong, R, and McGuire, J. 1993. Adsorption kinetics and elutability of a-lactalbumin, p-casein, p-lactoglobulin and bovine serum albumin at hydrophobic and hydrophilic interfaces. J. Colloid Interface Sci. 161 325-334. 

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