Spirulina platensis protein nanoparticle-based bigels: Dual stabilization, phase inversion, and 3D printing

Nanoparticle-based bigel is a miscellaneous emulsion system consisting of two immiscible gels, combining Pickering and bigel mechanism, which resulted in enhanced technological and functional outputs. The edible Spirulina platensis protein nanoparticle (SPNP)-based bigel with double network structure was prepared by homogenizing a hydrogel and an oleogel made from xanthan gum (XG) and sunflower wax (SW), respectively. Increasing oleogel/hydrogel (OG/HG) ratio led to phase inversion from O/W to W/O bigels as OG fraction ranged from 54 wt% to 60 wt%. XG network existed between oil droplets of O/W bigels and in the internal phase of W/O bigels, and SPNPs were adsorbed at W–O interfaces of all types of bigels (O/W, semibicontinuous, and W/O). Due to bigel formation depending on non-covalent interactions, it was summarized into a dual stability mechanism, both bigel and Pickering emulsion, combining interfacial and bulk stabilization in one system. These bigels displayed more superior to those bigels consisting of wax-based oleogel since the ideal printability regardless of only 5 wt% SW in OG. Owing to the effect of nozzle shearing of bigels after extrusion, all bigel inks showed a slight gather in the same phase and a significant decrease in hardness, springiness, cohesiveness, and gumminess after 3D printing, respectively. This study opens avenues for rationally designing novel plant-based products and offers a novel approach for the application of bigels as saturated fat replacers.