Interactions between casein layers adsorbed on hydrophobic surfaces from self consistent field theory: κ-casein versus para-κ-casein

Ettelaie, Rammile; Khandelwal, Niharika; Wilkinson, Rosemary

doi:10.1016/j.foodhyd.2012.09.006

Cited by 14 publications

(13 citation statements)

References 45 publications

(57 reference statements)

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“…The suffix “b” or “f” differentiate the two ends of the polymer chain from which the n monomers are chosen. The procedure for calculating the segment distribution functions for a given set of fields { ψ a ( r )} is well documented in the literature, as well as described in our own previous work . Therefore, this will not be reproduced here.…”

Section: Methodsmentioning

confidence: 99%

Fragmented proteins as food emulsion stabilizers: A theoretical study

2014

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Using a model based on the primary structure of  s1 -casein, the colloid stabilising ability of fragmented protein and that of the intact chains are compared. We perform Self Consistent Field (SCF) calculations to obtain the induced interaction potentials between the oil droplets, resulting from the overlap of adsorbed protein layers in each case. For the intact  s1 -casein, we confirm the known result, that the mediated inter-particle interaction potential develops a deep attractive energy minimum at high salt concentrations and pH values close to the isoelectric point of the protein. The same does not occur for the appropriately fragmented systems, with improved emulsion stability predicted as a result, even at pH values close to pI.It is shown that this superior performance, for the case considered, is due to the diblock-type behaviour of one of the fragments. On the other hand, it is well known that  s1 -casein more closely resembles the less favourable triblock structure. However, it is also demonstrated that the presence of a "diblock" like fragment by itself may not always be enough to produce a better emulsion stabiliser. It is seen that the hydrolysis of some peptide bonds may indeed lead to a suitable polypeptide, but that this is displaced from the interface by the structurally less desirable ones, also generated by the fragmentation process. The displacement occurs due to the competitive adsorption between different fragments. The removal of the undesirable fragments from the solution is found to greatly enhance the predicted colloid stabilising ability of the remaining polypeptide.

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Section: Methodsmentioning

confidence: 99%

Fragmented proteins as food emulsion stabilizers: A theoretical study

2014

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“…The actual details of the SCF method can be found in a number of key papers (Evers, Scheutjens, & Fleer, 1990, 1991Fleer, Cohen Stuart, Scheutjens, Cosgrove, & Vincent, 1993;Leermakers, Atkinson, Dickinson, & Horne, 1996;Scheutjens & Fleer, 1979, 1980 as well as in some of our own work Ettelaie, Khandelwal, & Wilkinson, 2014;Ettelaie, Murray, & James, 2003).…”

Section: Calculation Methodology and Models For Protein And Polysacchmentioning

confidence: 99%

“…The full detail of the calculations can be found in a number of references (Evers, et al, 1990;Fleer, et al, 1993;Leermakers, et al, 1996;Scheutjens, et al, 1980) including some of our previous work Ettelaie, et al, 2014;Ettelaie, et al, 2003). However, with functions G i f (n,z) and G i b (n,z) at hand, the concentration of each monomer species in every layer is can now be obtained from the composition law (Evers, et al, 1990;Fleer, et al, 1993) as follows:…”

Section: Calculation Methodology and Models For Protein And Polysacchmentioning

confidence: 99%

Colloidal interactions induced by overlap of mixed protein+polysaccharide interfacial layers

Ettelaie

Akinshina

2014

Food Hydrocolloids

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Colloidal interaction potentials induced by the overlap of mixed protein + polysaccharide interfacial layers, formed solely as a result of electrostatic attraction between these two biopolymers, have been calculated using the Self Consistent Field Theory. A significant difference between the nature and magnitude of these interactions, depending on the manner in which the charge is distributed along the length of the polysaccharide molecules, was predicted. For chains with an even distribution of charge, the repulsive interactions are in general weaker than those mediated by pure protein layers. For strongly charged polysaccharide chains, these become even attractive at a certain range of particle-particle separations. In part this is due to bridging by polysaccharides, occurring between opposite layers. However, in systems containing strongly charged polyelectrolyte, it is also the result of what in practice may be interpreted as a coacervate of protein + polysaccharide, with a tendency for aggregation, forming interfacial layers on the surface of the particles. In contrast, when the charge of the polysaccharide chains is unevenly distributed, the induced repulsive forces are much enhanced and become longer ranged compared to those for pure protein layers. Once the layers begin to overlap, the electro-steric interactions produced are found to completely overwhelm any van der Waals attraction, thus dictating the inter-particle interactions. We also present some preliminary calculations investigating the competitive adsorption of different polysaccharides onto the protein layer. The initial results, for polysaccharides of the same size and overall charge, suggest that the heterogeneously charged polyelectrolyte completely dominates the adsorption onto the surface, displacing all uniformly charged chains from the interface.

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“…With these additions accounted for, the final expression for the discretised form of (2) becomes [61,62] …”

Section: Methodsmentioning

confidence: 99%

First-order phase transition during displacement of amphiphilic biomacromolecules from interfaces by surfactant molecules

Ettelaie¹,

Dickinson²,

Pugnaloni³

2014

J. Phys.: Condens. Matter

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The adsorption of surfactants onto a hydrophobic interface, already laden with a fixed number of amphiphilic macromolecules, is studied using the self consistent field (SCF) calculation method of Scheutjens and Fleer. For biopolymers having unfavourable interactions with the surfactant molecules, the adsorption isotherms show an abrupt jump at a certain value of surfactant bulk concentration. Alternatively, the same behaviour is exhibited when the number of amphiphilic chains on the interface is decreased. We show that this sudden jump is associated with a first-order phase transition, by calculating the free energy values for the stable and the metastable states at both sides of the transition point. We also observe that the transition can occur for two approaching surfaces, from a high surfactant coverage phase to a low surfactant coverage one, at sufficiently close separation distances. The consequence of this finding for the steric colloidal interactions, induced by the overlap of two biopolymer + surfactant films, is explored. In particular, a significantly different interaction, in terms of its magnitude and range, is predicted for these two phases. We also consider the relevance of the current study to problems involving the competitive displacement of proteins by surfactants in food colloid systems.3

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Interactions between casein layers adsorbed on hydrophobic surfaces from self consistent field theory: κ-casein versus para-κ-casein

Cited by 14 publications

References 45 publications

Fragmented proteins as food emulsion stabilizers: A theoretical study

Fragmented proteins as food emulsion stabilizers: A theoretical study

Colloidal interactions induced by overlap of mixed protein+polysaccharide interfacial layers

First-order phase transition during displacement of amphiphilic biomacromolecules from interfaces by surfactant molecules

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