Lactoglobulin surface adsorption

At pH 7.0, Roscoe et al found that surface adsorption as measured by surface charge density was at the minimum value. This may be due partly to an increase in the volume of the )8-lactoglobulin structure during this denaturation from the compact globular structures at the lower pHs, resulting in a smaller packing density and hence decreased surface concentration. At pH 8.0, their experimental results showed an increase in the... 

Heat affects the conformation of proteins, and most proteins undergo fairly rapid heat denaturation somewhere between 333 and 363 A series of experiments was made by Roscoe and Fuller in which the surface adsorption behavior of bovine )8-lactoglobulin A, hen egg-white lysozyme and bovine pancreatic ribonuclease A was studied at a platinum electrode as a function of temperature using cyclic voltammetry. The protein solution and the electrochemical cell were separately immersed in the thermostated bath and allowed to equilibrate for 30 mins. The protein... 

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. 

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. ... 

Courthaudon, J.L., Dickinson, E., Matsumura, Y, and Clark, D.C. 1991a. Competitive adsorption of B-lactoglobulin -i- tween 20 at the oil-water interface. Colloids and Surfaces 56 293-300. 

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... 

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. 

Therefore, it can be concluded that the finite rate of the reorientation of P-lactoglobulin molecules in the adsorption layer, i.e. the oversaturation of the interfacial layer by molecules in an extended state (maximum molar area), leads to a faster surface tension decrease at low protein concentrations. At larger concentrations the reorientation step becomes less important and at higher concentrations (higher surface coverage) the adsorption process is completely described by the diffusional transport in the solution bulk. 

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. 

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