Viscoelastic behavior of wheat-sorghum composite flour dough using stress relaxation tests

The effect of wheat-sorghum flour ratio (0، 25، 50، 75 and 100%) on viscoelastic and farinographic behaviour of dough was investigated. Constants of Peleg - Normand model and the stress relaxation (% SR) was calculated for the variables and the correlation between farinograph characteristics and stress relaxation test parameters were evaluated. The results showed that with increasing the ratio of sorghum in flour، the amount of initial force (F0)، mixing tolerance index and the stress relaxation (% SR) increased. However، the rate of water absorption، dough stability and Peleg - Normand model parameters (K1 and K2) decreased with increasing substitution of sorghum flour. Survey results showed that the correlation between the parameters of water absorption، dough stability and K1 and K2 was a highly positive. The stress relaxation (% SR)، mixing tolerance index and the initial force (F0) had also positive correlations. With increasing substitution of sorghum flour، dough indicated the liquid-like viscoelastic behavior. Fitting the experimental data with the model showed the efficiency of Peleg - Normand model at high strain (10%).