Pickering high internal phase emulsions stabilized by protein-covered cellulose nanocrystals

The development of high internal phase emulsions (HIPEs) stabilized by food-grade particles (e.g., cellulose nanocrystals, CNCs) has attracted increasing interests in the food colloid field. This paper reports a type of oil-in-water HIPEs using protein (bovine serum albumin, BSA)-covered CNCs as effective stabilizers. The BSA-covered CNCs were simply obtained by mixing aqueous solutions of anionic CNCs with the cationic BSA at pH 3.0. Turbidity and absorption measurements proved the binding of BSA to CNCs. The strong interaction and aggregation of BSA-covered CNCs were verified by atomic force microscopy measurements. Interestingly, the 0.5% (w/v) CNCs covered with a low amount of BSA (0.01%–0.1%, w/v) as the emulsifying agent yielded very stable, gel-like HIPEs ( ϕ  = 0.8). The stiffness and microstructure of the HIPEs can be modulated either by changing the surface protein coverage at a fixed CNC concentration or by changing the concentration of CNCs with a fixed surface protein coverage (e.g., 80%). The improvement of the stiffness was largely attributed to the enhanced droplet packing effect and interfacial bridging effect. These findings offer a promising opportunity to extend the applications of protein-modified CNCs in the food and pharmaceutical industries.