Engineering interfacial and network structures in high internal phase Pickering emulsions: Mechanisms, encapsulation...

Bioactive compounds and probiotic cells are often limited in food applications by poor solubility, low stability, and restricted bioavailability. Emulsion-based delivery systems, particularly high internal phase emulsions, improve loading capacity and influence gastrointestinal behavior. Pickering emulsion gels stabilized by colloidal particles show enhanced interfacial stability and mechanical integrity compared to conventional emulsions. Their performance is determined by the interaction between particle design, interfacial assembly, and bulk network formation. This review analyzes Pickering emulsion gels and high internal phase systems from a structure-function perspective. It focuses on the roles of interfacial structure, droplet packing, and network organization in controlling encapsulation, digestion, and release. It also considers their use in processing technologies, including 3D printing as edible inks and 4D systems with stimulus-responsive behavior. Dense interfacial layers and jammed droplet networks increase encapsulation efficiency, limit molecular diffusion, and protect bioactives from environmental and oxidative degradation. Structural changes during digestion influence release kinetics, promote lipolysis, and improve bioaccessibility. Delivery performance depends on the balance between interfacial barrier strength and enzymatic accessibility. Highly organized and segregated structures allow co-encapsulation of hydrophilic and lipophilic compounds. In processing applications, these systems provide shear-thinning flow for extrusion and rapid structural recovery for shape retention. Stimulus-responsive systems support controlled release and functional changes such as color variation. However, performance is highly dependent on formulation and processing conditions. Future work should focus on combining interfacial design with scalable processing to develop reliable and application-oriented food systems.