Novel edible pickering high-internal-phase-emulsion gels efficiently stabilized by unique polysaccharide-protein hybrid nanoparticles from Okara

The development of high-performance and biocompatible Pickering stabilizers for O/W high internal phase emulsions (HIPEs) has attracted fast increasing interests in the food colloid areas, due to their potential applications in food and pharmaceutical formations. This work reports that a kind of nanoparticles (ISPN; with a size of about 160 nm), facilely fabricated by a high power ultrasonication treatment from the insoluble soy polysaccahrides of Okara (a byproduct of soybean processing), could perform as an outstanding Pickering stabilizer for HIPEs. The structure of the nanoparticles, mainly composed of polysaccharides and proteins, was stable over the test pH or ionic strength range (pH 2.0–12.0 or 0–500 mM). The formation, microstructure and rheology of the HIPE gels stabilized by the ISPN were investigated in terms of visual and microscopic observations, laser diffraction technique, and dynamic oscillatory measurements. The results indicated that the HIPE gels with soy oil as the dispersed phase could be formed at a particle concentration (c) as low as 0.25 wt%, and increasing the c (from 0.25 to 1.5 wt%) led to a progressive strengthening of their gel network, as well as a progressive decrease in their droplet size. The HIPE gels could be formed over the whole test pH (2.0–12.0) or ionic strength (0–500 mM) range, and their gel network could not be dispersed by 6.0 M urea or 1.0 wt% SDS. In addition, the fabricated HIPE gels exhibited an excellent stability upon a prolonged storage and heating at temperatures ranging from 50 to 90 °C, as well as an unique temperature responsiveness. All the observations demonstrated that the ISPN exhibited a great potential to perform as Pickering stabilizers for HIPEs, with the emulsification performance and ability to form the HIPE gels much better than those reported previously. The findings would be of interest not only for the development of a kind of novel edible HIPEs suitable for health food formulations, but also for guiding the high-added-value ultilization of the byproduct (Okara) of soybean processing industries.