ADSORPTION-KINETICS AND RHEOLOGICAL PROPERTIES OF FOOD PROTEINS AT AIR WATER AND OIL/WATER INTERFACES/

The behaviour of foams and emulsions stabilised by protein adsorption layers is controlled by the properties of the air/water or oil/water i nterface. Due to the dynamic conditions of these systems, the non-equi librium interfacial properties are dominant, such the formation of ads orption layers and their mechanical resistance. The adsorption kinetic s and thermodynamics of the food proteins beta-lactoglobulin and beta- casein are measured at the water/air and water/tetradecane interface b y using drop techniques. The equilibrium adsorption and the adsorption kinetics are discussed on the basis of a new theory which considers c hanging molar area of adsorbed proteins according to the surface cover age. The shear rheological behaviour of the systems is measured by usi ng an interfacial shear rheometer. The results complement each other a nd support the idea that the degree of unfolding of proteins depend on the surface coverage and thus changes with time and bulk concentratio n.