Co-effect of salt and sugar on extrusion processing, rheology, structure and fracture mechanical properties of wheat–corn blend

• Reducing salt and sugar resulted in an increase in extrudate expansion.
• Salt and sugar has synergistic effect on processing energy and mechanical strength.
• More porous structure was achieved with lower levels of salt and sugar.
• Effects of salt and sugar on processing and product parameters are not independent.

The effect of salt (0–2%) and sugar (0–10%) on the extrusion of wheat–corn blend was studied using a co-rotating twin screw extruder under the same processing settings. Reducing salt and sugar levels increased torque, die pressure and specific mechanical energy. The increased die pressure resulted in higher expansion of the extrudate with more porous structure. This was particularly evident when both salt and sugar were eliminated in the formulation. Reducing salt and sugar did not appear to influence the shear viscosity of the melt except when eliminated from the formulation. Similarly the maximum force to fracture the extrudates was also not significantly affected, except when salt and sugar were removed completely. Salt and sugar has synergistic effect on processing energy, extrudate expansion and mechanical strength. This provided a potential to decrease the sugar and salt in extruded products but still maintain textural quality.