Investigation of intestinal lipolysis and lutein release in structured lipid droplet via microfluidics: Influence of...

Lipid digestion is governed by the oil-water interface, and the dynamic changes in droplet structure and lipolysis continuously modify the interface, which makes it difficult for conventional techniques to resolve the regulatory mechanisms. Herein, microfluidics was employed to control the reaction interface and elucidate the effects of oleogel crystals on lipid lipolysis and lutein release. Structured lipid droplets were individually captured in microfluidic traps, enabling real-time visualization of lipolysis and lutein release at the single-droplet level. Multiple microscopy techniques were employed to characterize droplet structural evolution and lipolysis behavior. Bright-field and polarized light microscopy confirmed successful droplet capture and revealed crystalline structures within oleogel droplets, while fluorescence microscopy enabled real-time monitoring of morphological changes and fluorescence evolution during digestion. Lipolysis kinetics were quantified from droplet size changes, and lutein release was evaluated based on fluorescence intensity variations. Results demonstrated that higher crystallinity resulted in delayed free fatty acid release and decreased lutein release amount. The regulatory role of oleogel crystal crystallinity on lipid lipolysis during digestion was confirmed. Isothermal titration calorimetry showed that elevated crystallinity enhanced heat release but reduced entropy and spontaneity during lipase-emulsion interactions, which might be associated with conformational changes of lipase. These findings suggest that oleogel crystals are likely to affect lipolysis efficiency by inducing conformational changes in lipase at the oil-water interface. This study provided novel insights for the advancement of oleogel digestion mechanisms as well as scientific evidence for rational design of lipid-based functional foods.