Bambara groundnut (Vigna subterranea) modifies structural, physicochemical, nutritional, and glycemic properties of instant sago noodles

• Sago and Bambara groundnut are climate-resilient crops adaptable to climate change and suitable as local carbohydrate sources. • The addition of Bambara groundnut improves the nutritional composition of sago noodles. • Sago–Bambara noodles have higher nutritional value than commercial wheat flour noodles. • Noodles with 40% Bambara groundnut exhibit a low glycemic index. • Sago and Bambara groundnut noodles can serve as alternative products to support food and nutritional security. Climate change underscores the need to diversify staple foods toward climate-resilient crops that promote both nutritional adequacy and metabolic health. Sago ( Metroxylon sp.) and Bambara groundnut ( Vigna subterranea ) are underutilized climate-resilient crops with strong potential for sustainable food innovation. This study developed instant sago noodles fortified with Bambara groundnut flour and evaluated their nutritional composition, microstructural characteristics, and glycemic index (GI) in comparison with conventional wheat noodles. Four formulations were prepared, i.e. 100% sago (F0) and sago substituted with 30% (F1), 40% (F2), and 50% (F3) Bambara groundnuts. Proximate composition, dietary fiber fractions, starch characteristics, cooking properties, SEM and FTIR profiles, and in vivo glycemic responses (ISO 26642:2010) were assessed. Bambara groundnut substitution significantly increased protein, fat, dietary fiber, and resistant starch contents (p<0.05), while reducing total starch level. The 40% Bambara groundnut substitution exhibited the most acceptable cooking quality and a balanced nutritional profile, containing 9.73, 11.05, and 11.94% protein, dietary fiber, and resistant starch, respectively. Structural analyses indicated enhanced starch–protein–fiber interactions without altering the fundamental starch structure. In vivo GI testing (n=10) demonstrated that F2 achieved a low GI (49±4.84), significantly lower than 100% sago noodles (56±8.12) and comparable to commercial wheat noodles (46±4.83). Overall, Bambara groundnut–fortified sago noodles represent a nutritionally improved, low-GI, and climate-resilient alternative to wheat-based products, supporting dietary diversification and metabolic health.