Analysis of eating quality and nutritional properties of millet reconstituted rice

Foxtail millet ( Setaria italica L .) is a nutrient-rich minor grain widely favored for developing healthy staple foods. However, few studies have systematically characterized the comprehensive quality variations of extruded millet-rice reconstituted rice under gradient foxtail millet incorporation. In this work, twin-screw extrusion was applied to fabricate reconstituted rice with five foxtail millet substitution ratios (0%, 20%, 40%, 60%, 80%, and 100%). A series of indicators covering nutritional composition, cooking properties, surface appearance, texture profiles and in vitro digestibility were measured to clarify the regulatory effect of millet proportion on the nutritional and edible quality of extruded reconstituted rice. The results demonstrated that increasing millet proportion significantly raised the contents of crude fat, crude protein, linoleic acid, linolenic acid, acidic amino acids and neutral amino acids ( P < 0.05). Meanwhile, lightness ( L *) decreased, while redness ( a *) and yellowness ( b *) increased continuously. Cooking loss first declined and then elevated, reaching the minimum value at 80% millet substitution; by contrast, water absorption and swelling power grew steadily with the rise of millet ratio. Higher millet dosages promoted the conversion of weakly bound water to tightly bound water and improved the water retention capacity of the matrix. V-type amylose–lipid complexes (type 5 resistant starch, RS5) were identified in all samples, and the 80% millet group possessed the maximum relative crystallinity of 7.08%. Scanning electron microscope results showed that the 80% millet sample formed a uniform and compact starch matrix filled with evenly distributed tiny micropores, while the 100% millet group exhibited loose, broken structures with large cavities. The 60% millet group had the lowest gumminess and chewiness as well as the highest overall sensory score. The content of rapidly digestible starch (RDS) differed remarkably among groups. RDS reached its peak at 60% millet substitution and decreased sharply at 80%, whereas slowly digestible starch (SDS) and RS stayed relatively stable across all treatments. In summary, 60% millet substitution yields preferable texture and sensory performance for daily eating, while the 80% millet sample presents the highest V-type crystallinity and outstanding hypoglycemic capacity. This study systematically reveals the multi-scale quality evolution of extruded reconstituted rice regulated by millet addition, and provides theoretical basis and technical support for the development of low-glycemic, nutrient-fortified millet functional staple foods.