Effect of cooking on the drying behaviour of tarhana dough, a wheat flour-yoghurt mixture

Drying behaviour of tarhana dough before and after simmering at atmospheric pressure for 10 min was studied by changing the drying temperature (60-80 degreesC) and sample thickness (1-6 mm). The cooking process accelerated the drying process possibly due to increased porosity of dough by starch gelatinization, Fick's equation was used to calculate the diffusion coefficient for water (D-eff) at different sample thicknesses. An increase in D-eff values was observed at increased sample thickness for both normal and cooked dough. The D-eff values for cooked dough were higher when compared to normal dough. Activation energies were calculated using an Arrhenius type equation to determine the effect of drying temperature on D-eff values. It was found that D-eff values are more sensitive to changes in drying temperature during drying of normal tarhana dough than during that of a cooked dough cooked, suggested by higher activation energies for normal tarhana dough. (C) 2002 Elsevier Science Ltd. All rights reserved.