The current project aims at elucidating how bile salts (BS) structure influences their interfacial behaviour and their impact on fat digestion. Neutron reflectivity (NR) is the only technique that can provide a detailed molecular picture of the BS/lipids interface, over time and at equilibrium. We have measured the interactions of two distinct BS, sodium taurocholate and sodium taurodeoxycholate, with a lipid film at the air/water interface, using the Langmuir trough and NR techniques. We will be complementing these studies with NR at the oil/water interface, which reflects the actual fat droplet/water interface. We now propose to use NR at the oil/water interface with two glyco-conjugated BS, sodium glycocholate and sodium glycodeoxycholate, to confirm our assumption that BS interfacial behaviour is mostly linked to the bile acid portion, i.e., the position and number of hydroxyl group.