Analysis of Dough Sheeting and Heat Transfer during Baking of Unleavened Flat Bread (Chapathi).

Unleavened Indian flat bread (Chapathi) is widely consumed by a large section of the population. An automatic unleavened flat bread making device (Chapathi) is designed and developed; it consists of a sheeting and a baking device. The prototype device is used for the preparation of Chapathis. The observations made during these experimentations are used for the improvement of the device. The sheeting characteristics of Chapathi dough prepared from Atta and whole wheat flour with varying levels of water is studied. The trials indicated that the consistency of the dough to be about 110 s for Atta and 120 s for whole wheat flour and the pressure required to extrude the dough to be in the range 3.43*105 4.41*105 Pa. It is observed that 0.8*10-3 m slit width is optimum to get a Chapathi sheet thickness of 1.5*10-3 m. Individual modes of heat transfer are estimated for the baking of Chapathi. Mathematical expressions are proposed for the heat transferred to and absorbed by Chapathi during baking. Thermal conductivity of Chapathi is determined and found to be in the range 0.29 0.35 W/m 0C. It is noted that out of the 236.25 W of heat absorbed by the Chapathi, approximately 151.06 W is the latent heat of evaporation of water while sensible heat is about 86.12 W. The heat transfer analysis clearly indicates significant contribution from conduction, which is crucial for the characteristic flavor and crustiness of the Chapathi. Thermal efficiency of the Chapathi baking oven is estimated to be about 51 %. [ABSTRACT FROM AUTHOR]