Dynamic and static properties of proteins adsorbed at the air/water interface

Abstract

The adsorption of /3-and K-casein at the airlwater interface from solutions containing concentrations ranging from lo-' to 10-1 weight % has been monitored using both radiotracer and ellipsometric techniques. The surface pressure and dilatational modulus have also been measured both during the adsorption process and at steady state conditions. Differences between the surface properties of ,8-and K-casein are related to the structures of the molecules. The adsorption data cannot be described by Gibbs' adsorption equation. The adsorption isotherms and film thicknesses are discussed in terms of the distribution of amino-acid residues between trains and loops. At low surface coverage where loop formation is not pronounced, theories based on polymer statistics describe the relationships between film pressure, dilatational modulus and surface coverage satisfactorily. At low surface concentrations of protein the dilatational modulus is purely elastic whereas at higher surface concentrations it has both elastic and viscous components.

Fenugreek Galactomannans as Food Emulsifiers

“…It was therefore concluded that the proteinaceous matter does not have any significant effect on the surface activity of the fenugreek gum. This conclusion may draw criticism from the scientific community, in view of the fact that other gums lost their activity upon removal of protein from the native gum (16,19,20). More experimental work is needed to further purify the gum or to isolate the active proteinaceous-associated structures that are surface active.…”

“…It can be demonstrated that at gum/oil ϫ 100 values of R c > 12, the emulsions were stable and free of flocculation for a long time ( Table 2). The oil to gum critical ratio required to obtain efficient droplet coverage, R c , was compared to other galactomannans and found to be smaller, reflecting more efficient interfacial coverage, (20,18 and 12 for LBG, guar and fenugreek gum, respectively). It was therefore concluded that fenugreek is more efficient than the other galactomannans in stabilizing oil-in-water emulsions.…”

The Effect of pH on Monoglyceride–Caseinate Mixed Monolayers at the Air–Water Interface

“…This phenomenon could be of practical importance in food formulations (such as ice cream) where milk proteins and monoglycerides are used as emulsifiers. As caseinate is a composite of four different proteins, the individual caseins, although similar to each other, have somewhat different properties and this is reflected in their interfacial behavior at the fluid-fluid interfaces and in the stability of emulsions (32)(33)(34).…”

Adsorption kinetics and dilatational rheological studies for the soluble and anchored forms of alkaline phosphatase at the air/water interface

“…Contributions were made by several research groups, [11][12][13][14][15][16][17] using different experimental set-ups. Among the developed techniques, the harmonic drop oscillation associated with axisymmetric drop shape analysis (ADSA) is currently commercially available.…”