Heat and Mass Transfer in Cookie Baking

This study, started in August 2003, was supported byTUBITAK-TOGTAG (The Scientific and Technological Research Council of Turkey – Agriculture, Forestry & Veterinary Research Grant Committee)with a project number of TOGTAG-3201, and completed in February 2005.

Eren Demirkol (Masters Student) was involved in this project.

Abstract

Increasing trade of ready to eat foods such as cookies highlights an interest in quality defects during baking. It is very expensive to apply microwave or radio frequency to form a volume heating to increase quality. Since baking involves a simultaneous heat and mass transfer involving diffusion and conduction inside and convective heat and mass transfer outside, accurate values of heat and mass transfer parameters should be known for optimization purposes. Therefore, changes in these parameters during baking of cookies were investigated. For this purpose, cookies, prepared with AACC Method 10-50D, were baked at 190, 200 and 210 °C under natural and forced convection conditions and the required parameters were determined.

Moisture content and humidity ratio difference approaches as a driving force for mass transfer were applied for mass transfer coefficient calculations, and use of humidity ratio difference approach seemed to be better in terms of reflecting actual process conditions. Diffusion coefficients were found to vary with baking time and temperature. Then, variable heat transfer coefficient values for the bottom and top surface of the cookies was determined. The results of this study showed that use of realistic approaches is significant to determine the actual values of heat and mass transfer parameters. These parameters might also be used for modeling and optimization of baking processes to produce high quality products.