Development of Extruded Millet Analogue Rice: A Comparison of Rheological, Structural, Physiochemical, and Cooking Properties with Conventional Rice

Millet analogue rice was made from pearl millet, sorghum, and parboiled rice by using extrusion technology. The impact of extrusion process conditions in terms of screw speed (9–15 rpm), feeder speed (7–11 rpm), die temperature (80–100 ◦C), and materials moisture content (28–32%wb) on cooking characteristics, viz., cooking losses (CL), cooking time (CT), and water absorption ratio (WAR), and physiochemical properties, viz., water absorption index (WAI) and water solubility index (WSI) were assessed to obtain a quality millet analogue rice using a central composite design of the RSM model. The model showed that die temperature and materials moisture content exhibited the most significant effects on the dependent parameters. The optimized process condition of 28%wb moisture content, 12 rpm screw speed, 7 rpm feeder speed, and 80 ◦C die temperature showed 5.67% CL, 942.82 s CT, 2.155% WSI, 7.093 g/g WAI, and 6.815 WAR with the desirability value of 0.858. Millet analogue rice exhibited a significant difference (p < 0.05) on the textural properties, proximate analysis, and physical characteristics when related to the raw rice. The crystallinity index of millet analogue rice was lower than that of raw rice with similar FTIR spectral patterns and showed surface cracks and internal voids during SEM analysis. Practical applications: The global prevalence of diabetes is increasing rapidly as a consequence of consumption of foods with high glycemic index (GI), which raises the blood glucose level. Rice flour-based products and white rice are not a good choice of food for people with diabetes due to their high GI value. Therefore, millet analogue rice was developed from pearl millet, sorghum, and parboiled rice as a substitute for rice using the hot extrusion method. This produced millet analogue rice can be an alternative food for raw rice and has a scope for commercialization in the market.