Effect of temperature and composition on thermal conductivity of "Mlinci" dough

Abstract

The objective of this study was to determine the thermal conductivity of "Mlinci" dough T-500 and "Mlinci" dough T-500 with the addition of eggs, wheat germs and wheat bran in the temperature range of 40°C to 70°C. Thermal conductivity was determined using modifications of guarded hot plate steady state method. For all types of dough, thermal conductivity first increased with temperature and then, after reaching maximum values, it decreased. The maximum values for "Mlinci" dough T-500 containing wheat germs and bran were 54°C, and for "Mlinci" dough T-500 with eggs were 58°C. The minimal value of 0.347 ± 0.020 W/mK was determined for "Mlinci" dough T-500 at 39.38°C. The maximum value 0.585 ± 0.023 W/mK was determined for "Mlinci" dough T-500 with wheat bran at 54.39°C. The thermal conductivity of "Mlinci" dough T-500 with the addition of wheat germs and wheat bran was higher in comparison with the basic composition due to the elevated amounts of ash, water, proteins, and porosity, as well as non-homogeneity. Based on the experimental thermal conductivity values of "Mlinci" dough T-500 samples at various temperatures, quadratic polynomial equations were developed. The research results could be used for the modelling of the heat transfer of "Mlinci" dough T-500 during processing.