Novel nanoparticles from insoluble soybean polysaccharides of Okara as unique Pickering stabilizers for oil-in-water emulsions

Abstract

The development of biocompatible Pickering stabilizers for oil-in-water emulsions has attracted fast increasing interests, due to their potential applications in food and pharmaceutical formulations. This work reports that a kind of novel nanoparticles to perform as outstanding Pickering stabilizers can be facilely fabricated from insoluble soybean polysaccharides (ISP) of Okara (a byproduct of soybean processing) by a high power ultrasonication. The ultrasonication resulted in breakdown of polysaccharide-based fibres in the ISP, and subsequently, formation of nanoparticles with sizes of 127–221 nm. The nanoparticles were mainly composed of polysaccharides and proteins, possessing a lower crystallinity of cellulose (relative to ISP) and good interfacial adsorption at oil-water interface. They were demonstrated to exhibit an excellent emulsification performance and a high tendency to form a gel-like network in the Pickering emulsions. Increasing the particle concentration and/or oil volume fraction was favorable for the creaming stability of the emulsions. Most of the droplets in the emulsions at higher particle-to-oil ratios were present in a more flocculated state, which was maintained by the hydrophobic interactions, as well as a bridging particle monolayer (with two droplets sharing the same monolayer). Interestingly, a portion of fine oil droplets with sizes <0.1 μm were entrapped within the flocculated structure consisting of large droplets with sizes at around 8 μm, which might largely account for the excellent emulsification performance of these nanoparticles. The findings would be of importance not only for the development of a kind of food grade nanoparticles to perform as outstanding Pickering stabilizers for the emulsions, but also for providing a strategy for the highly-added-value utilization of Okara.