Impact of high shear extrusion on the structural and rheological properties of cereals, pseudocereals, and legume flours

Extrusion cooking is an efficient technology used in food industry to modify the structural and functional properties of raw materials, enhancing their applicability in food formulations. This study evaluated the effect of high shear extrusion on the structural and rheological properties of flours derived from cereals (rice, oats, sorghum), pseudocereals (quinoa, amaranth), and legumes (chickpea, lentil, black bean, pinto bean). Changes were analyzed using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, Mixolab, and dynamic-oscillatory rheology. FTIR revealed loss of starch short-range order and changes in the protein conformation, with transitions in the secondary structures. XRD confirmed reduced crystallinity and increased amorphous content after extrusion, reflecting starch gelatinization. Mixolab analysis showed significant increases in initial cold consistency and stability torque in extruded flours, indicating enhanced water-flour interactions, and formation of a cohesive matrix with resistance under mixing stress. Retrogradation torque decreased across all extruded flours, which reflect a reduced capacity to form harder gels after a heating treatment, compared to raw flours. Rheological evaluations demonstrated increased viscoelastic moduli in most extruded flours, when compared to their raw counterparts which was linked to starch gelatinization and protein interactions. Sorghum, quinoa and legumes exhibited superior pseudoplastic behavior, highlighting their stability during processing. In conclusion, results demonstrated the potential of high-shear extrusion to enhance the structural and functional properties of flours from cereals, pseudocereals, and legumes, enabling the development of clean-label ingredients with improved and diverse functionality for industrial applications. • High-shear extrusion modifies starch and protein conformation in cereals and pseudocereals. • FTIR and XRD showed less crystallinity and more amorphous content, varying by grain. • Extruded oat, rice, and quinoa flour showed higher cold consistency and less retrogradation. • Rheological tests indicated grain-dependent viscoelastic and pseudoplastic after extrusion. • Extrusion produces multifunctional ingredients tailored to the structure of each raw material.