Surfactant-free cellulose filaments stabilized oil in water emulsions

There has been significant interest over recent years in the production and application of sustainable and green materials. Among these, nanocellulose has incurred great interest because of its exceptional properties and wide range of potential applications, including in Pickering emulsions. However, the production cost of these cellulosic materials has limited their application. In this study, the capability of a new type of cheaper cellulosic material, cellulose filaments (CFs), in formulating stable oil in water Pickering emulsions was investigated and compared with three conventional nanocelluloses, namely cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs) and TEMPO-oxidized CNFs (TEMPO-CNFs). Results showed that CFs can provide stable surfactant-free emulsions over wide ranges of salt concentration (0-500 mM) and pH (2-10), as indicated by the near-constant oil droplet size and dewatering index of the emulsions. This is due to the ability of CFs to strongly adsorb to the oil and water interface, as evidenced by Cryo-SEM and visualized through labelled CFs with engineered carbohydrate-binding module (CBM2a) conjugated with green fluorescent protein (CBM2a-eGFP) under fluorescent microscopy. Compared to the emulsions stabilized by other types of nanocelluloses, the CF-stabilized emulsion demonstrated a larger average droplet size and comparable (with CNFs) or better (than CNCs and TEMPO-CNFs) stability, which is partially attributed to the higher viscosity of continuous phase in the presence of CFs. The results of this study demonstrate the use of CFs as a novel and cheaper cellulosic material for stabilizing emulsions, which opens the door to a range of markets from the food industry to engineering applications. [GRAPHICS] .