DYNAMIC SURFACE-TENSION AND SURFACE SHEAR RHEOLOGY STUDIES OF MIXED BETA-LACTOGLOBULIN TWEEN-20 SYSTEMS

The mechanical behaviour of beta-lactoglobulin (BLG) and BLG/Tween 20 adsorption layers at the air/water interface has been studied by dynam ic surface tension and surface shear theological measurements. The ads orption properties were measured using different surface tension metho ds (ring tensiometry, drop volume tensiometry and axisymmetric drop sh ape analysis). The surface shear theological measurements were perform ed with a torsion pendulum set-up which simultaneously provides inform ation about the surface shear viscosity and elasticity. The adsorption layer structure is controlled by the interactions between protein and surfactant molecules. The corresponding dynamic surface tension measu rements confirm the peculiarities foun adsorption layer. With increasi ng surfactant concentration at constant protein concentration the mixe d surface film gradually approaches a state identical to a pure surfac tant adsorption layer, from which the protein is completely repelled.