Effect of the Sugar Replacement by Citrus Fibre on the Physical and Structural Properties of Wheat-Corn Based Extrudates

Citrus fibre was used as a substitute for sucrose in the formulation of wheat-corn-based extrudates produced using twin screw extruder. Replacing 5 % sugar with an equal quantity of fibre resulted in an increase in die pressure, torque and specific mechanical energy (SME), and consequently the expansion ratio increased. A further increase in fibre content to 10 % (e.g. reducing sugar to 0 %) had little effect on the extrusion processing parameters. The microstructure of extrudates examined by X-ray computed tomography shows that the porosity of the extrudates increased with increasing fibre content, which was attributed to an increased number of large pores. As the citrus fibre content increased, the maximum force required to fracture the extrudate increased; however, the cell wall thickness decreased. This suggests that the fibre component may have contributed to the strength of the cell wall. This study demonstrated a potential utilisation of fibre from by-product of juice extraction as a source of dietary fibre in low sugar-extruded products.