Hybrid particles for stabilization of food-grade Pickering emulsions: Fabrication principles and interfacial properties

Colloidal particles have garnered considerable research attention in recent times for fabrication of Pickering emulsions because of their distinctive ultra-stabilization properties in comparison to conventional emulsion stabilizers. Significant progress has been made in designing novel hybrid particles, i.e., a combination of two or more materials comprising the particles, for tailoring emulsion stability as well as other functionalities that are not achievable with single particle-laden interfaces. We aim to provide a critical survey of the latest advances in food-grade hybrid particles that have been used to prepare Pickering emulsions in this review with an emphasis on the engineering of hybrid particles through various physical and chemical synthesis routes. In particular, we have examined the hybrid protein-polysaccharide, protein-phenolic compound, polysaccharide-lipid particles that have surfaced in the last five years with respect to their ability to stabilize and provide additional functionalities to PEs. We discussed recent studies on interfacial characterization of hybrid particles using interfacial (tension, rheology, Langmuir Blodgett), adsorption (quartz crystal microbalance with dissipation monitoring), microscopy and X-ray scattering techniques. Synthesis of hybrid particles primarily depends on the properties of biopolymers: hybrid particles fabricated using water-insoluble biopolymers such as insoluble plant proteins exploit anti-solvent precipitation methods, whilst fabrication using water-soluble components usually involve covalent (alkaline treatment/oxidation/Maillard) or ionic interactions. Hybrid particles stabilize PEs via a combination of denser interfacial layer formation as well as bulk stabilization and offer benefits in protection/release of active lipidic ingredients versus single particle stabilizers.