Recent advances on cellulose nanocrystals for Pickering emulsions: Development and challenge

Pickering emulsions stabilized by solid particles have captured a growing interest recently due to their outstanding stability. Among various solid stabilizers, cellulose nanocrystals (CNCs) mainly from agricultural and forestry wastes have emerged as promising materials in Pickering emulsions application due to their favorable properties such as nanostructure, high aspect ratio, biocompatibility, amphiphilicity, low toxicity, and renewability. In this review, the source and extraction methods of CNCs are summarized briefly. Then, the recent advances in CNCs stabilized Pickering emulsions are highlighted, including the factors affecting the emulsification performance of CNCs itself and the synergistic effect induced by other substances. Furthermore, the food-related research, safety issue and the promising research trends of CNCs stabilized Pickering emulsions are also outlined. The properties of CNCs mainly depend on the cellulose sources and extraction processes. The morphology, surface charge, wettability and crystalline allomorph of CNCs can influence emulsifying ability as Pickering stabilizers. The synergistic effect induced by other substances (i.e. polysaccharide, protein, polyphenol, lignin, surfactant, and inorganic particle) increases potential of CNCs in Pickering emulsions application. The food-related research of CNCs stabilized Pickering emulsions currently focuses on delivering bioactive compounds, improving stability and controlling lipid digestion. Future studies could devote more efforts to effective and green extraction of CNCs, revealing stabilization mechanism in a multicomponent system and developing functional applications of CNCs-based Pickering emulsions. In addition, the safety assessment involving CNCs and their stabilized emulsions deserves more attention for food-related applications.