Back extrusion properties of wheat porridge (Dalia) Original Research Article

The effects of wheat grits and sugar concentrations and temperature on the rheological characteristics of wheat porridge were investigated using the back extrusion method. Wheat porridge (Dalia) was prepared with addition of grits at concentrations of 10%, 12.5% and 15% and sugar at levels of 0%, 6% and 12% in distilled water. The porridge was back extruded at temperatures of 20°C, 40°C and 60°C. Plunger speeds varying from 100–2500 mm/min were used so that the porridge could be back extruded over a wide range of shear rates. The force displacement data were used to determine the consistency coefficient and flow behaviour index. The study revealed the non-Newtonian and pseudoplastic behaviour of wheat porridge. Wheat grits concentration had the most pronounced effect on the consistency followed by temperature and sugar concentration. Consistency coefficient increased with increasing grits and sugar concentration but decreased with increasing temperature. The consistency coefficient of the porridge samples varied from 5.9 to 241.6 Pa sn and the activation energy varied from 9.23 to 33.57 kJ/g mol. The porridge samples exhibited yield stress only at the highest grits concentration of 15% and lowest temperature of 20°C.