Interface and Bulk Phase Engineering in Water-in-Oil High Internal Phase Emulsion: A Clean-Label Strategy for Stabilization and Application

Abstract

The integration of water into food systems as water-in-oil (W/O) high internal phase emulsions (HIPEs) offers a promising approach to reduce fat content and facilitate bioactive delivery. However, their thermodynamic instability, driven by extensive interfacial areas and mobile water phases, poses significant formulation challenges. It is significant to develop clean-label stabilizers to replace synthetic surfactants to stabilize W/O HIPEs. This review examined the design principles of W/O HIPEs, based on the clean-label concept, with a focus on how interfacial and/or bulk phase engineering influenced the stability and functionality of emulsions. It provided a comprehensive overview of natural ingredients and biopolymer-based particles/microgels, focusing on their roles in fat replacement, bioactive encapsulation, controlled release, and novel material applications. Major challenges in W/O HIPEs included phase inversion and separation, underscoring the need for effective stabilizer designs. Traditionally, polyglycerol polyricinoleate (PGPR) has been used as a stabilizer, but its synthetic nature and potential toxicity drive demand for clean-label alternatives. The combination of particles with biopolymers can enhance the hydrophobicity and emulsification, reducing PGPR reliance. Additionally, the use of biopolymers to thicken or gel the oil and water phases can further restrict droplet mobility, mitigating phase separation. Dual-stabilization approaches with the integration of interfacial and bulk stabilizers offer great potential to enhance the kinetic stability of emulsions. However, controlled destabilization in W/O HIPEs can be advantageous, improving oral lubrication, bioactive/flavor release, and 3D printing adaptability. Future efforts should prioritize plant-based stabilizers, synergistic mechanisms, and structural dynamics during processing and oral consumption to scale clean-label W/O HIPEs.