Effect of Bile Salts on the Interfacial Dilational Rheology of Lecithin in the Lipid Digestion Process.

The effects of bile salts on the emulsifier adsorption layer play a crucial role in lipid digestion. The current study selected sodium cholate (NaCh) and lecithin as model compounds for bile salts and food emulsifiers, respectively. The interface dilational rheological and emulsification properties of NaCh and lecithin were carried out. The results showed that the NaCh molecules could quickly diffuse from the bulk to interface, which broke the tightly-arranged interfacial layer of lecithin and enhanced the viscoelasticity of interfacial film. As a result, the interfacial adsorption layer, which was originally dominated by the slow relaxation processes within the interface, was transformed into one controlled by the fast molecular diffusion exchange. This accelerated the exchange of materials between the bulk and interface, thereby creating suitable conditions for the interfacial adsorption of lipases, which promoted the digestion process. These results provided a mechanism for the promotion of lipid digestion by bile salts from the perspective of interfacial viscoelasticity and relaxation processes. A deeper understanding of the interfacial behavior of bile salts with emulsifiers would provide a basis for the rational design of interfacial layer for modulating lipid digestion.