Cellulose Nanocrystal-Based Pickering Emulsions as Advanced Biomaterials for Food Bioactive Delivery: Chemical Modification, Synergistic Stabilization, and Functional Applications

Cellulose nanocrystals (CNCs) are renewable and biodegradable nanomaterials that can stabilize Pickering emulsions through steric hindrance and electrostatic repulsion. However, pristine CNCs show limited interfacial anchoring because of their strong hydrophilicity and high surface charge density, making the emulsions susceptible to coalescence, phase separation, and structural instability under environmental stresses. This review summarizes two major strategies for stabilizing and functionally regulating CNC-based Pickering emulsions: chemical modification and synergistic stabilization. Chemical modification regulates CNC surface charge, wettability, interfacial anchoring, and functional group composition through oxidation, amination, esterification, graft copolymerization, desulfation, and etherification, whereas synergistic stabilization constructs composite interfacial films or continuous-phase networks through noncovalent interactions between CNCs and proteins, polysaccharides, cyclodextrins, surfactants, inorganic nanomaterials, or functional molecules. The ability of these emulsion systems to compartmentalize oil-soluble bioactives within structured droplets also provides a basis for improving bioactive stability and release behavior in food-related formulations. These strategies improve emulsion stability and introduce antibacterial, antioxidant, responsive, and controlled-release properties, highlighting the potential of CNC-based Pickering emulsions in active food systems, including food preservation, active packaging, and the stabilization, protection, and release regulation of food bioactives. Remaining challenges in green preparation, structural regulation, release mechanisms, scalable production, and practical evaluation are also discussed.