Baking-drying kinetics of crisp bread: The influence of bran content and baking temperature

In this study، mathematical modeling of hot air baking-drying of thin-layer crisp bread was investigated. Thin-layer drying process were conducted under three different temperatures of 110، 150 and 190 °C at a constant air velocity of 0. 5±0. 1 m/s and absolute humidity of 0. 6 ± 0. 04g water/kg dry air. It was found that the baking-drying process occurred in falling rate period over the baking-drying times. Eight well-known thin-layer baking-drying models were fitted to the baking-drying experimental data of crisp bread، implementing non-linear regression analysis techniques. Based on the coefficient of determination (R²) and root mean square error (RMSE) values، it was concluded that the best models in terms of fitting performance for hot air baking-drying of bran free crisp bread were Wang & Singh and Logarithmic while for whole-wheat crisp bread were Page، Logarithmic and Wang & Singh. The moisture transfer from crisp bread was described using the Fick’s diffusion model. The effective diffusivity was within the range of 2. 88×10-8 to 1. 11×10-7 m2/s for bran free crisp bread and from 2. 47×10-8 to 8. 84×10-8 m2/s for whole-wheat crisp bread over the temperature range. The activation energy for bran free and whole-wheat crisp bread was found to be 25. 22 and 23. 43 kJ/mol، respectively..