Evaluating the printability and digestibility of 3D-printed pea-sorghum protein gels

This study explored the 3D printability and digestibility of pea and sorghum protein gels as novel plant-based bioinks. First, 25% sorghum protein gel (SPG25) and 15-25% pea protein gels were prepared, and the effect of extruders’ nozzle size on printability was evaluated. Samples produced at the optimized conditions were then used for analyzing particle size, microstructure, secondary structure, and in vitro digestibility. Pea protein gel at 20% (w/w) (PPG20) and SPG25 showed ideal rheological properties, including shear-thinning behavior and rapid recovery. Dual-nozzle 3D printing was optimized at a nozzle diameter of 0.52 mm and a speed of 10 mm/s, resulting in a layered PPG20–SPG25 structure. Pea proteins and their gels showed degrees of protein hydrolysis in the range of 83.1-89.4%, while sorghum proteins exhibited degrees of hydrolysis of 50.3-51.5%. When they were 3D-printed together (3D-PPG20–SPG25), their hydrolysis was 10% higher compared to that of the unprinted mixture. FTIR analysis revealed changes in secondary structure as the α-helix to β-sheet ratio in printed gels (1.82) was higher than that of the mixture of PPG20-SPG25 (0.87). SEM imaging showed distinct globular morphology and smoother surfaces at gel interfaces. These structural modifications likely resulted from 3D printing-induced changes in microstructure and protein secondary structure at the interfaces of gels. This is the first study to integrate hydrophilic and hydrophobic plant proteins in a 3D-printed layered format and link print-induced conformational changes to digestibility. • 3D-printed pea–sorghum gels showed ideal rheology and structural stability. • Optimized dual-nozzle printing (0.52 mm, 10 mm/s) created a layered 3D structure. • 3D printing improved digestibility by 10% vs. unprinted pea–sorghum mixtures. • FTIR/SEM showed structural changes upon 3D printing, impacting digestibility.