Fabrication and characterization of rice bran oil-in-water Pickering emulsion stabilized by cellulose nanocrystals

Abstract

An agricultural residue, defatted rice bran (DRB), was used as a cellulosic source in the isolation of cellulose nanocrystals (CNCs) under sonication (CNC-Dso) or conventional stirring (CNC-Dst), and hydrolysis with 55% sulfuric acid. The morphological investigation of CNCs from CNC-Dso showed a needle-like structure with an average cross diameter and length of 12.7 and 327nm, respectively. The CNCs from CNC-Dso were used as a stabilizer for rice bran oil-in-water (o/w) Pickering emulsions, incorporated with a non-ionic surfactant (PG1.5SFR0.05) and gum arabic. The characterization of the stabilized o/w emulsions was evaluated by visual inspection, confocal laser scanning microscopy (CLSM), particle size analysis, surface coverage, and rheology. The synergistic effect of 2.5wt%PG1.5SFR0.05 and 0.25wt% CNC-Dso produced the highest stability of emulsion, with the smallest mean diameter and monodisperse droplets. However, the presence of gum arabic led to polydispersity and a larger droplet size. The rheological data provided evidence of gel-like behavior in all emulsions. The effect of CNC-Dso on inhibiting the degradation of unsaturated fatty acids by retarding the change of peroxide was measured using Image J software. These results suggest the possibility of using a relationship between these biopolymers to stabilize o/w emulsions. This is important for the application and production of solid particle-based emulsions.