Self-similar assemblies of globular whey proteins at the air-water interface: effect of the structure.
We investigated the structure of heat-induced assemblies of whey globular proteins using small angle neutron scattering (SANS), static and dynamic light scattering (SLS and DLS), and cryogenic transmission electron microscopy (Cryo-TEM). Whey protein molecules self-assemble in fractal aggregates with a structure density depending on the electrostatic interactions. We determined the static and dynamic properties of interfacial layer formed by the protein assemblies, upon adsorption and spreading at the air-water interface using surface film balance and interfacial dilatational rheology. Upon spreading, all whey protein systems show a power-law scaling behavior of the surface pressure versus concentration in the semi-dilute surface concentration regime, with an exponent ranging from 5.5 to 9 depending on the electrostatic interactions and the aggregation state. The dilatational modulus derived from surface pressure isotherms shows a main peak at 6-8 mN/m, generally considered to be the onset of a conformational change in the monolayer, and a second peak or a shoulder at 15 mN/m. Long-time adsorption kinetics give similar results for both the native whey proteins and the corresponding self-similar assemblies, with a systematic effect of the ionic strength.
INRA-BIA, BP 71627, 44316 Nantes Cedex 3, France. najet.mahmoudi@unifr.ch
Najet
N
Mahmoudi
Cédric
C
Gaillard
François
F
Boué
Monique A V
MA
Axelos
Alain
A
Riaublanc
D000388:Air; D020285:Cryoelectron Microscopy; D004548:Elasticity; D045703:Emulsifying Agents / Q000737:chemistry; D008894:Milk Proteins / Q000737:chemistry*; D033363:Neutron Diffraction; D009994:Osmolar Concentration; D011312:Pressure; D055503:Protein Multimerization; D055550:Protein Stability; D012212:Rheology; D053838:Scattering, Small Angle; D055672:Static Electricity; D013499:Surface Properties; D013500:Surface Tension; D014867:Water; D000067816:Whey Proteins
D045703:Emulsifying Agents; D008894:Milk Proteins; D000067816:Whey Proteins; D014867:Water