Galactomannan-rich ingredients from Caesalpinia pulcherrima seeds reorganize wheat bread microstructure and enhance technological and nutritional quality

Galactomannan-rich ingredients from tropical legumes are promising biomaterials to design bakery products with improved structure and nutritional quality. This study evaluated the structure–function relationships of Caesalpinia pulcherrima seed flour (FSF) and seed gel (GSF) in wheat bread. A central composite design assessed the effects of FSF (3.96–11.04%) and GSF (0.17–5.82%) on technological properties, proximate composition and microstructure. FSF and GSF increased loaf specific volume (from 2.16 to 3.87 mL g⁻¹), alveoli number and circularity, while maintaining expansion index values comparable to the control, indicating improved gas retention without impairing dough expansion. FSF-enriched breads showed higher protein (up to 17.28%), lipid (up to 10.11%), ash and fiber contents than the control, confirming FSF as the main contributor to nutritional enrichment, whereas GSF mainly affected hydration and crumb structure. pH, moisture and water activity remained within typical ranges for pan bread and compatible with standard yeast fermentation. SEM and CLSM images revealed a more continuous and cohesive gluten–starch matrix with thinner cell walls and more uniform gas cells in enriched crumbs, aligning with the improved technological performance. Overall, FSF and GSF act as functional biomaterials that valorize an underutilized tropical legume and support the development of nutritionally enhanced, structurally tailored wheat breads.