This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Rice and lentils are a pairing that goes a long way back, whether as khichdi in India or mujaddara in the Middle East. On its own, each is a source of incomplete protein, short on certain essential amino acids—but paired together, they fill each other's gaps, and lentils also blunt white rice's high glycemic index.
Extrusion-based 3D food printing, which builds edible shapes by squeezing paste through a nozzle layer by layer, has mostly used processed cereal-legume ingredients. Refined starches and protein isolates behave predictably in the nozzle, and hydrocolloids such as xanthan gum are often added generously to hold prints together. Producing these, however, costs energy and chemicals, and hydrocolloids in large doses can ruin the taste.
Whole flours, by contrast, are unpredictable, as their own proteins, fats and fibers all push and pull on how a paste flows. A team of researchers from Singapore University of Technology and Design (SUTD), led by Professor Chua Chee Kai and Associate Professor Tan U-Xuan, wanted to know whether white rice and red lentil flours could be used to print and cook well with small additions of wheat flour, tapioca flour and a trace of xanthan gum. The motivation was partly personal.
"I grew up in a vegetarian household where rice and lentils were staple food choices, well before the term 'plant-based' became commonplace," said SUTD Research Associate Aakanksha Pant, lead author of the study published in Innovative Food Science & Emerging Technologies. "Transforming minimally processed flours into visually appealing yet nutritionally balanced 3D shapes was exciting, as it combines food, material science, design and additive manufacturing." The team ground red lentils into flour and blended it with rice flour, oil, seasonings and water, testing 11 formulations before retaining three. "Printability was characterized by precision and shape stability," explained Phoebe Leam Xin Ni, a Ph.D. student at SUTD who is also part of the research team.
"Inks with a smooth extrusion profile that produced uniform, well-adhered prints and held their shape for 30 minutes after deposition were classified as successful." One ink used rice and lentil flours alone. A second swapped part of the rice for tapioca flour and added xanthan gum at just 0.05% by weight. A third combined rice, tapioca and wheat flours.
All three thinned under the shear of the nozzle and thickened again once deposited. The xanthan gum ink retained the most water and was marginally the most reluctant to flow, yet it clumped during printing. The other two inks produced neater butterfly and cloud shapes.
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