Interfacial Characterization of β-Lactoglobulin Networks : Displacement by Bile Salts

The competitive displacement of a model protein (β-lactoglobulin) by bile salts from air−water and oil−water interfaces is investigated in vitro under model duodenal digestion conditions. The aim is to understand this process so that interfaces can be designed to control lipid digestion thus improving the nutritional impact of foods. Duodenal digestion has been simulated using a simplified biological system and the protein displacement process monitored by interfacial measurements and atomic force microscopy (AFM). First, the properties of β-lactoglobulin adsorbed layers at the air−water and the olive oil−water interfaces were analyzed by interfacial tension techniques under physiological conditions (pH 7, 0.15 M NaCl, 10 mM CaCl2, 37 °C). The protein film had a lower dilatational modulus (hence formed a weaker network) at the olive oil−water interface compared to the air−water interface. Addition of bile salt (BS) severely decreased the dilatational modulus of the adsorbed β-lactoglobulin film at both th...