Nanocellulose is the most abundant natural shape-anisotropic nanoparticle extracted from plant cell walls, offering promising prospects as a particle stabilizer of Pickering colloids and emulsions for applications in food, cosmetics, and green materials. In this study, cellulose nanofibrils (CNF) was used as a depletion stabilization inducer to stabilize cellulose nanocrystal-based low-oil-concentration Pickering emulsions with droplet size being micrometers. Ultra-long, thin, and flexible CNF was mainly distributed in aqueous phase as flocs, showing a high efficiency to induce concentration-dependent depletion effect. Upon increasing the concentration of CNF, the creaming behavior of CNC-stabilized Pickering emulsions transformed from regular creaming without flocculation (low CNF), over creaming containing highly flocculated droplets (medium CNF), to stable emulsions with small-sized droplet aggregates (high CNF). The droplets flocculation at medium CNF was mainly induced by depletion flocculation. Above critical stabilization concentration, the size of flocculated droplets becomes independent of CNF concentration, and emulsion stabilization was achieved by depletion stabilization and emulsion gel mechanism. The universal feasibility of current system was demonstrated by employing dodecane as oil phase, displaying similar droplet phase behavior as sunflower oil. The depletion interaction in Pickering emulsions induced by rod-like biopolymer was proved to be rod-length dependent. The findings could be of importance to researches and applications of flexible biopolymers in all-natural label-friendly Pickering colloidal dispersions. The results of this study also provide valuable information for food-grade emulsion manufacturers who would like to use all-natural materials within their products to realize high-stability, low-oil-concentration, and fluid-like emulsion products, e.g., beverage or soft drinks.

Stabilization of cellulose nanocrystal-based Pickering emulsion induced by cellulose nanofibrils: Impact of depletion effect on the phase behavior of emulsion droplets

255th National Meeting (2018)

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