Review of advanced structural strategies for controlling lipid digestion in emulsion‑based delivery systems

Structurally diverse emulsion systems play a pivotal role in improving the delivery, stability, and digestion of lipophilic nutrients in food and pharmaceutical applications. This review aims to compare the in vitro digestion behaviours and barrier mechanisms of various emulsion types, including surfactant-based, Pickering, gel-based, dried, and complex emulsions. A literature-based approach was adopted, emphasising findings from studies using standardized in vitro digestion models, particularly the INFOGEST protocol. Key parameters evaluated include lipid hydrolysis, bioaccessibility, and the structural features that influence enzyme access and digestion kinetics. Surfactant-based emulsions typically show rapid lipolysis, often reaching >70–90% free fatty acid (FFA) release, whereas Pickering and gel-based emulsions can reduce or delay digestion, with some systems limiting FFA release to ~30–60% depending on particle packing and gel matrix density. Dried emulsions exhibit variable behaviour depending on reconstitution efficiency, while complex emulsions offer tunable and sustained release profiles. These findings highlight the importance of interfacial engineering, matrix entrapment, and structural integrity in modulating digestive fate. In conclusion, selecting appropriate emulsion structures allows targeted control of nutrient release and bioavailability. Appropriate emulsion design enables controlled nutrient release and better bioavailability for next-generation functional emulsions.