Real-time tracking of the adsorption and degradation behavior of bovine serum albumin, casein, and fibrinogen on the lipid layer by optical interferometry

Different kinds of proteins interact with the digestible lipids in various ways, affecting the adsorption behavior of proteins and digestion. The ordered porous layer interferometry (OPLI) system was constructed by the silica colloidal crystal (SCC) films used to monitor the real-time binding assessment between bovine serum albumin (BSA), casein, fibrinogen, and triolein. The OPLI system reflected the changes in protein mass on the SCC films in real time through the migration of the interference spectrum of the SCC films, which was converted into the changes in optical thickness (ΔOT) that can be monitored. OPLI systematically studied the degradation of proteins by trypsin and found that the lipid layer enhanced the hydrolysis of trypsin to BSA and fibrinogen but weakened the degradation of trypsin to casein. The high OT of the lipid layer (10.45 nm) indicated that trypsin was more likely to adhere to the casein surface on the lipid layer than to hydrolyze casein. In contrast, the reduced OT (−6.40 nm) on the SCC films indicated that trypsin was more inclined to hydrolyze casein than to attach to casein. The OPLI system provided the technical basis for real-time tracking of protein hydrolysis behavior in complex food systems.