Thermo-mechanical pre-treatments modulate the structure, protein and starch digestibility, and thermal and pasting properties of sorghum flour

This study examined the effects of five thermal-mechanical pre-treatments, including popping, roasting, parboiling, pressure cooking, and extrusion, on the structure, digestibility, and thermal and pasting properties of sorghum flour. The results indicated that dry-heat treatments disrupted the starch-protein matrix, which caused granule swelling, fusion and partial gelatinisation. Protein digestibility was highest after extrusion (76.2 %) and lowest in pressure-cooked sorghum flour (42.6 %). Wet-heat treatments, including parboiling and pressure cooking, consistently increased thermal stability, as evidenced by higher onset and peak temperature (To, Tp) and enthalpy changes (ΔH), while roasting resulted in the lowest ΔH, consistent with partial gelatinisation. FTIR analysis revealed protein unfolding, particularly in dry heat-treated samples, and SEM imaging showed changes in the morphological microstructure, confirming granule swelling and formation of an amorphous matrix. These findings underscore the potential of these treatments to enhance the properties of sorghum flour and broaden its use in food products.