Effect of 3D printing conditions and post‐printing fermentation on pearl millet fortified idli

BACKGROUND Three‐dimensional (3D) printing is an emerging technology with numerous applications in the development of novel foods to meet personalized and special dietary needs. Using 3D printing, foods with modified textures and consistency can be prepared conveniently. In this work, an indigenous rice–black gram batter was fortified with pearl millet flour and 3D printed in the in‐house developed extrusion‐based food printer, Controlled Additive‐manufacturing Robotic Kit (CARK™). The impact of material supply composition was investigated along with optimization of different printing parameters and an in‐depth analysis of post‐printing fermentation kinetics was undertaken. The shape changes in the 3D printed constructs during fermentation were analyzed using a pixel‐count‐based image‐processing technique that correlates with the change in surface area. RESULTS The addition of millet flour resulted in accelerated fermentation. At 20% w/w level, better printability with higher precision and layer definition was obtained at 800 mm min−1 of printing speed, 360 rpm extrusion motor speed, and 1.22 mm nozzle diameter with an extrusion rate of 15.57 mm3 s−1. The constructs of pearl millet flour (PMF) fortified idli batter have shown good structural stability and creep recovery. Fermentation‐assisted shape change was found to be significantly influenced by infill levels. Both raw and steamed constructs with 40% infill showed around 37% lower hardness than 100% infill constructs due to a porous inner structure with reduced expansion in the surface area/volume during fermentation. CONCLUSION The results of the study provide insights into the scope of printing fermented foods through the food‐to‐food fortification approach and textural modification of foods using 3D printing by varying the infill levels. © 2022 Society of Chemical Industry.