Lipolysis products formation during in vitro gastric digestion is affected by the emulsion interfacial composition

Abstract In this work, we report on the effect of the emulsion interfacial composition on the lipid digestion kinetics of in vitro gastric lipolysis. Emulsions (o/w) were formulated with triolein (5%, w/w) and emulsifiers of different chemical nature (1%, w/w). These emulsifiers included different low-molecular-weight surfactants: sodium taurodeoxycholate (NaTDC, ionic), soy lecithin (LEC, zwitterionic), and tween 80 (TW80, non-ionic); as well as biopolymers: soy protein isolate (SPI) and citrus pectin (CP). Emulsions were subjected to static gastric in vitro digestion. Samples were characterized as a function of digestion time in terms of physicochemical properties (droplet charge, microstructure and particle size analysis) and multiple lipolysis products (HPLC coupled to a charged aerosol detector). The kinetic analysis, based on the % of digested triolein, showed that emulsions stabilized by biopolymers did not represent a barrier for gastric lipase adsorption, reaching the highest extents of lipid digestion (25–28%) in the gastric phase. Emulsions stabilized by low-molecular-weight surfactants presented considerable different behaviors under gastric conditions: lipolysis extents of NaTDC- and TW80-based emulsions were low due to early instability or strong interfacial displacement of gastric lipase, respectively; while the LEC-based emulsion presented a higher lipolysis extent (15%) due to its stability and apparent moderate interfacial displacement of gastric lipase. The quantification of multiple lipolysis products allowed the validation of the gastric lipolysis molecular mechanism previously proposed. The results hereby presented constitute advanced insight in the effect of interfacial design on the kinetics of in vitro gastric lipid digestion.