Cultivating edible bio-inks: Elevating 3D printing with medium-internal-phase emulsion gel incorporating soybean protein isolate microgel particles

In response to changing dietary preferences and increasing health consciousness among consumers, the food industry is gradually moving toward healthier and higher-performance edible bio-inks. This study prepared soybean protein isolate microgel particles (SPIMP) using dynamic high-pressure microfluidization (DHPM) as a pretreatment method. Under DHPM pressure, the average particle size of SPIMP progressively decreased from 609.6 nm to 254.8 nm, accompanied by an increased interfacial adsorbed protein content of 81.78% and 91.49%. Contact angles of native SPI were measured at 70.1 degrees +/- 0.6 degrees, while those for microgel particles were 78.1 degrees +/- 0.2 degrees, 80.3 degrees +/- 0.7 degrees, and 84.5 degrees +/- 1.2 degrees, respectively. These SPIMP were then utilized to formulate a medium-internal -phase emulsion gel with an oil fraction of 50%. Microscopic analysis and examination of chemical interaction forces revealed that the network structure of the emulsion gel primarily formed through inter-droplet hydro-phobic interactions and the formation of disulfide bonds. This enhancement contributed to the gel strength and water retention capacity of the emulsion. Rheological tests confirmed the outstanding shear-thinning properties and high viscoelasticity of the emulsion gel, positioning it as a promising edible bio-ink for 3D printing. Experimental printing further substantiated its suitability, confirming extrudability, printing performance, and self-supporting properties. Notably, the medium-internal-phase emulsion gel-based reduced-fat surimi products demonstrated better suitability for 3D printing within real food systems compared to traditional surimi products. This study introduced innovative approaches for producing medium-internal-phase emulsion gel with superior 3D printing properties, significantly expanding the potential for the development of edible bio-inks.