Preparation of soybean protein isolate-rice bran oil bigels and their 3D printing potential for dysphagia foods

3D printing has emerged as a promising technology for developing nutritional foods to meet the needs of people with dysphagia. However, a single hydrogel or oleogel cannot meet the strict performance requirements for 3D printing, while bigels are ideal inks by combining the merits of both gels. In this study, soybean protein isolate (SPI)–rice bran oil (RBO) bigels were prepared at oleogel/hydrogel ratios of 30:70, 40:60, 50:50, 60:40, and 70:30. The samples were characterized by confocal laser scanning microscopy (CLSM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), rheology, texture profile analysis (TPA), low-field nuclear magnetic resonance (LF-NMR), liquid binding capacity (LBC), oxidative stability, International Dysphagia Diet Standardisation Initiative (IDDSI) tests, and manual extrusion using a 3D printing pen. Increasing oleogel content promoted phase evolution from oil-in-water (O/W) to bicontinuous and water-in-oil (W/O) structures, enhanced hydrogen-bonding-related spectral changes and crystallinity, and reduced free-water mobility. All formulations showed shear-thinning behavior and elastic-dominant networks. Among them, BG6 (60:40) showed the most balanced performance, including the highest thermal stability (Tpeak = 55.17 °C), high LBC (98.68%), relatively slow lipid oxidation, IDDSI Level 5 compliance, and visually stable F-, Z-, and cube-shaped structures under manual extrusion. These results suggest that SPI-RBO bigels, particularly BG6, have potential as plant-based edible inks for dysphagia-oriented 3D printed foods under the tested conditions.