The role of bread in economy and nutrition of human life has always been inevitable. Becouse it contains all of the necessary nutritional elements.Iranian bread posess good nutritional characteristics. Among the Iranian breads, the Sangak bread has a distingish nutritional value and a special taste. Due to inappropriate production conditions a gread deal of Iranian traditional breads are being wasted away. One of the major reasons of this problem is their quick staling. Part baking i.e. carrying out gelatination and coagulation of gluten, without any color changes in the crust is one of the most effective ways to retard staling. These products are highly vulnerable and should be freezed and kept in frozen form. For a better design of refrigeration systems, engineering calculation and modeling of the process is necessary. In the first part of this work, thermophysicel properties (thermal conductivity, specific heat, enthalpy, initial freezing temperature and density) were determined and modeled. The results showed that the initial freezing point for part baked Sangak bread was -2.5°C, and Krisher model can be used to predict the thermal conductivity values as a function of temperature. In the second step, the staling of the frozen part baked Sangak bread during storage at -20°C until 3 months, after thawing (immediately, 24h and 48h after thawing) and final baking (immediately, 24h and 48h after final baking) was determined. The results of puncture test during 3 months of storage showed no significant staling in frozen part baked Sangak breads, however after thawing and final baking, the breads were significantly staled after 48h. Finally, a mathematical model was developed using Fourie’s second law of conduction by finite difference method based on Enthalpic scheme. High correlation between experimental data and model predicted values shows that the model is able to predict temperature profiles in different parts of bread during freezing with a good precision. Key words: Part Baked, Sangak, Heat transfer, Phase change, Freezing, Staling
