Baking of Flat Bread in an Impingement Oven: An Experimental Study of Heat Transfer and Quality Aspects

Abstract

A new impingement oven was designed and tested for its thermal and quality performance for baking of thin flat bread. The test facility was instrumented to monitor and record during the baking process. Bread temperature and weight loss were recorded on-line during baking at oven temperatures of 150, 175, 200, 225, and 250 C and 1, 2.5, 5, 7.5, and 10 m/s jet velocities, respectively. Image processing was used for monitoring the bread volume and surface color changes during baking. Better baking conditions were obtained with the impingement oven in comparison with the conventional direct fired ovens. Experiments showed that a higher jet velocity can be used for flat bread baking at lower oven temperatures and yield shorter baking times for the same quality product. For very thin breads (such as the Iranian breads), results show that conduction heat transfer from the bottom surface of the tray must also be considered along with the convective heat transfer from the jets in selection of optimal operating parameters. It is noted that desirable baking conditions, e.g., good browning, uniform color, high volume increase, etc., can be achieved in a well-designed and operated impingement oven in shorter baking times compared to the conventional ovens.

Baking of Flat Bread in an Impingement Oven: Modeling and Optimization

“…In an earlier experimental study, these values were discussed thoroughly. [6] The crumb temperature, as stated before, must reach 100 C in order for the process of starch gelatinization to be completed. Starch gelatinization is the most important quality attribute of the bread that contributes to the sensory acceptability in terms of appearance and texture.…”

“…As stated before, this quantity describes the color as well as lightness of the bread. [6] Therefore, DE equal to 17.5 was taken as the most desired for flat breads.…”

“…Experimental results also provided us with such information but in discrete values of input variables. [6] Therefore, using the modeling results rather than experimental ones, the trade-off between quality attributes was studied more accurately and comprehensively.…”

“…More details of the constructed oven, measurement methodology, and data acquisition system may be found in previous papers by the same authors. [6,15] All of the baking experiments lasted for 25 min, which provided comprehensive information to investigate the baking process until combustion or charring occurred.…”

“…An earlier paper presented the experimental results of the variation of quality attributes as the baking control parameters were changed. [6] However, the experiment does not provide continuous information required for more detailed analyses such as finding the optimum point at which all of the quality indexes are satisfied.…”