Effect of oil and particles content on microstructure, rheology, and thermosensitive 3D printability of particles -stabilized high internal phase Pickering emulsions

In this study, soybean protein isolate (SPI) microgel/chitosan (CS) blending system prepared by gel fragmentation were used as particle-based emulsifiers. The presence of chitosan significantly reduced the particle size of the particles and decreased their contact angle (from 129° to 102°), thereby enhancing their wettability. These particles adsorbed onto the oil-water interface by rapidly decreasing the interfacial tension, forming stable O/W-type high internal phase Pickering emulsions. Confocal laser scanning microscopy analysis showed that the droplets were tightly packed together, and some of them were observed to have a polyhedral shape due to the packing, which is the basis for the formation of self-supporting structures. The rheological properties are closely related to the 3D printing results, increasing the oil and particles concentration improves the viscosity, energy storage modulus and gel strength of the system, while the excellent thixotropy facilitates the ability to 3D print these emulsions. At an oil content of 75% and a particles concentration of 3.0%, the accuracy and stability of the printed models were 97.9% and 99.2%, respectively. Introduction of curcumin and NaHCO₃ led to a color change from yellow to reddish-brown during heating, enabling thermosensitive 3D printing of color changing HIPPEs. This study may broaden the range of applications of plant-based HIPPEs in 3D and thermosensitive 3D printing, as well as for the development of other innovative food products.