Cellulose nanocrystals from ultrasound process stabilizing O/W Pickering emulsion

Abstract

Cellulose nanocrystals (CNC) are bio-based solid particles arisen as promising stabilizers for Pickering emulsions in food, pharmaceutical and cosmetics industries. This study aimed to understand the stabilization mechanism of oil-in-water emulsion using CNC as stabilizing particles. CNC were obtained from cellulose microcrystalline after acid hydrolysis, dialysis, ultrasound treatment and vacuum filtration. Atomic force microscopy (AFM) showed needle-shaped CNC. The CNC presented good stability against agglomeration due to the high electrostatic repulsion between particles, making them feasible to be used in O/W emulsions. O/W emulsions were stabilized by CNC and prepared using rotor-stator and ultrasound as mechanical processes. Emulsions stabilized by CNC were opaque, homogeneous and kinetically stable during few days. Small droplets generated during the ultrasound process, could be covered by cellulose nanoparticles that acted as an effective mechanical barrier against droplets coalescence in a Pickering mechanism. The mechanism of droplets stabilization was associated with electrostatic and steric repulsion between droplets. Emulsions were evaluated varying the proportion between flaxseed oil and cellulose nanocrystals (CNC). Emulsions with a lower proportion of CNC showed better kinetic stability compared to emulsions with higher CNC proportion. After 7 days of storage, the viscosity of emulsions with a higher proportion of CNC particles decreased, which was associated to the emulsion destabilization. Our results improved the understanding of the relationship between the proportions of oil and particles for emulsion properties by evaluating the potential application of CNC as a food emulsifier.