Lactoglobulin protein adsorption

Adsorption kinetics, mainly studied by dynamic surface tension measurements, shows many features very much different from that of typical surfactants (Miller et al. 2000). The interfacial tension isotherms for standard proteins such as BSA, HSA, (3-casein and (3-lactoglobulin were measured at the solution/air interface by many authors using various techniques. The state of the art of the thermodynamics of adsorption was discussed in Chapter 2 while isotherm data for selected proteins were given in the preceding Chapter 3. Here we want to give few examples of the dynamic surface pressure characteristics of protein adsorption layers. 

The structure of adsorption layers is of great importance during preparation of food foams and emulsions. These problems have been studied in [144] for protein adsorption at the liquid/gas interfaces and in [145] for liquid/liquid interfaces. Due attention is also paid to the interaction of typical emulsifiers and proteins during preparation of food emulsions [146 - 147]. Addition of an oil-soluble emulsifier to proteins during preparation of w/o emulsions [146] increased the emulsification rate, but at high concentrations decreased it due to the increase in oil viscosity. In this case, the emulsifier displaced (3-casein from the surface easier than P-lactoglobulin. However, there was no complete displacement into the aqueous phase since multiple emulsions were formed, as mentioned above [142 -143]. Hence, the ehoice of the surfactant/protein ratio is important. 

Protein adsorption to PS latex has also been determined by sedimentation field flow fractionation (SdFFF). The maximum surface coverages of P-casein and p-lactoglobulin on negatively charged PS latex calculated using this method were similar at around Img/m [19]. This figure, which was confirmed by amino acid analysis of the material irreversibly bound to the surface, was significantly lower... 

Bedford, E.E., Boujday, S., Humblot, V., Gu, F.X., Pradier, C.-M., 2014. Effect of SAM chain length and binding functions on protein adsorption P-lactoglobulin and apo-transferrin on gold. Colloids Surf. B Biointerfaces 116, 489—496. 

Landstrom, K., Alsins, J., Bergenstahl, B., 2000. Competitive protein adsorption between bovine serum albumin and 3-lactoglobulin during spray-drying. Food Hydrocolloids 14(1) 75-82. 

Lin et al. [24] studied adsorption-desorption isotherm hysteresis exhibited by /-lactoglo-bufin A on a weakly hydrophobic surface. They found that the desorption isotherm at pH 6.0 overlapped with the adsorption isotherm and that the adsorption-desorption process of /-lactoglobulin A under this condition could be characterized by a fully reversible Langmuir model. The desorption isotherm at pH 4.5, however, did not coincide with the adsorption isotherm, giving rise to hysteresis. This would suggest that protein adsorption experiments carried out under mild conditions of pH at relatively hydrophilic siufaces might be treated with the assumption that reversible equihbrium exists between the bulk and interface. 

The adsorption of albumin from aqueous solution onto copper and nickel films and the adsorption of B-lactoglobulin, gum arabic, and alginic acid onto germanium were studied. Thin metallic films (3-4 nm) were deposited onto germanium internal reflection elements by physical vapor deposition. Transmission electron microscopy studies indicated that the deposits were full density. Substrate temperature strongly Influenced the surface structure of the metal deposits. Protein and/or polysaccharide were adsorbed onto the solid substrates from flowing... 

The supercooling is also observed with protein (BSA, casein, lactoglobulin) in addition to the aqneous phase-Cjg system, bnt the freezing point of hexadecane increases to 18.2°C. This indicates that the crystallization of the hexadecane is affected by the presence of surface-active molecules. The supercooling will have extensive dependence on various interfaces, such as emulsions, oil recovery, and immunological systems. The adsorption of proteins from aqueous solutions on snrfaces has been studied by neutron reflection. ... 

The surfactant /1-lactoglobulin is a small protein molecule that does not strongly unfold upon adsorption at the O-W interface (Section 10.3.2). Consequently, stability against aggregation will primarily be due to electrostatic repulsion. The dilution with water will lower the ionic strength by about a factor of 2. It can be seen in Figure 13.4 that this will cause a considerable increase in W, e.g., by a factor of 50. Moreover, the larger W value will cause an increase in the value of D, which will also increase the gel time. 

Dalgleish, D.G., Euston, S.E., Hunt, J.A., and Dickinson, E. 1991. Competitive adsorption of 3-lactoglobulin in mixed protein emulsions. In Food Polymers, Gels and Colloids, ed. 

The interfacial behavior of protein-surfactant complexes is important in several areas such as the stability of emulsions and foams and the adsorption of proteins and surfactants from their binary solutions onto solid surfaces. Of particular interest is the adsorption of the milk proteins /3-lactoglobulin and /3-casein at the oil-water interface in the presence of nonionic surfactants in relation to food emulsions [56-58] and foam stability [59]. The adsorption of gelatin at the air-water [52,53,60], oil-water [6], and solid-water [62] interfaces in the presence of surfactants has also been studied. Other studies reported include adsorption from aqueous solutions of lysozyme plus ionic surfactants at solid surfaces [63,64], /3-lactoglobulin plus SDS onto... 

Figure 7 The adsorption of sodium n-dodecylsulphate (SDS), /3-lacto-globulin, and /3-lactoglobulin from a mixture of 0.1% w/v protein plus 0.5% w/v SDS onto methylated silica as a function of degree of dilution. 0, pure SDS Q, pure /3-lactoglobulin O, SDS + /3 lactoglobulin. The open symbols are adsorption after 30 minutes, and the closed symbols are adsorption after 30 minutes of rinsing. Solvent 0.01 M phosphate buffer, pH 7 plus 0.15 M sodium chloride. (Reproduced from Wahlgren and Amebrant [65] with permission from Academic Press.)...

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