The Effect of Baking Time and Baking Temperature on Porosity, Density and Thermal conductivity of the Part-Baked Sangak Bread, during Baking

Sangak bread, for its nutritional value, aroma, and special taste has a high potential to be industrially mass produced and supplied to the market,part-baked. In this paper, the effect baking temperature (in four levels of: 230, 250, 270 and 290 degrees Celsius) on the moisture content, porosity, apparent density andthermal conductivity during special times of baking (in30, 60, 90, 120, 150, 180 seconds) in the part-baked Sangakbread were studied. The performed tests indicated asignificant reduction of moisture and apparent density as the result of increasing the baking temperature. Theresults of tests show a significant increase in porosity with the increase in baking time and baking temperature. The effective thermal conductivity was measured using the thermal conductivity probe. Based on the results of the test, the increase in baking temperature, due to theireffects on increase in porosity and reduction of moisture content, causes reduction in the thermal conductivity. In this paper, four models (Series, Parallel, Krischer , and Maxwell) were developed for describing the thermal conductivity. The effective thermal conductivity data predicted with Krischer model were really compatible with the experimental data. In addition, the distribution factor (fλ) was evaluated by using Krischer model. Results showed an increase in this parameter with the increase in baking time and baking temperature.

Keywords:

Thermal conductivity , Thermal conductivity model , Line heat source , Porosity , Image processing , apparent density