Human lipid digestion begins at the interface of oil and water by interfacial adsorption of lipases. Tailoring the available surface area for lipase activity can lead to specific lipid sensing in the body, thus, tailored satiety hormone release. In this study we present biopolymer layers at the MCT-oil/water interface with different stabilities under human gastric environment (37 degrees C, pH 2, pepsin). Physicochemical changes and enzymatic degradation of interfacial layers were monitored online by interfacial shear rheology. We show the weakening of beta-lactoglobulin (beta-lg) layers at body temperature and acidification and their hydrolysis by pepsin. If sufficient concentrations of nanocrystalline cellulose (NCC) are given to an existing beta-lg layer, this weakening is buffered and the proteolysis delayed. A synergistic, composite layer is formed by adding methylated NCC to the beta-lg layer. This layer thermogels at body temperature and resists hydrolysis by pepsin. Coexistence of these two emulsifiers at the air/water interface is evidenced by neutron reflectometry measurements, where morphological information are extracted. The utilized layers and their analysis provide knowledge of physicochemical changes during in vitro digestion of interfaces, which promote functional food formulations.