Effect of Superheated Steam Pretreatment on Cooking, Functional, Structural, and Nutritional Properties of Millet-Based Rice Analogue

Abstract

The present study investigated the effect of superheated steam (SS) pretreatment on the functional, cooking, nutritional, and structural properties of a millet-based rice analogue (MBRA). SS pretreatment was applied at temperatures of 120, 140, and 160°C for treatment times of 10, 20, and 30 min prior to extrusion processing. The produced MBRA samples were evaluated for hydration behavior, cooking quality, texture, pasting properties, microstructure, crystallinity, and nutritional characteristics. SS pretreatment significantly influenced the overall quality attributes of MBRA (p < 0.05). Increasing treatment intensity enhanced starch modification, resulting in a progressive increase in Water Absorption Index (WAI), Water Solubility Index (WSI), and Water Absorption Ratio (WAR), along with a reduction in cooking time. Among the treatments, SS at 140°C for 20 min showed the most balanced improvement, yielding a WAI of 4.74 g/g, WSI of 14.68%, cooking time of 21.96 min, WAR of 4.62, and cooking loss of 12.36%. Structural characterization revealed reduced starch crystallinity, while FTIR exhibited distinct spectral shifts in the fingerprint region, along with the formation of a denser and more compact microstructure with fewer pores. These structural modifications contributed to improved textural properties and enhanced pasting behavior of MBRA. Additionally, SS-pretreated MBRA showed significant improvements in nutritional characteristics compared with the untreated control, indicating enhanced nutritional functionality. Overall, superheated steam pretreatment demonstrated strong potential as a clean and efficient pre-processing strategy for improving the cooking, functional, structural, and nutritional quality of millet-based rice analogue.