An Innovative Micro-Modelling of Simultaneous Heat and Moisture Transfer during Bread Baking Using the Lattice Boltzmann Method |
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Authors: | Mohamed Ahmed Hussein Thomas Becker |
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Institution: | 1.Group of (Bio-) Process Technology and Process Analysis, Faculty of Life Science Engineering,Technische Universit?t München,Freising,Germany |
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Abstract: | A considerable fraction of the energy consumed in bread manufacturing is used for the baking process. A thorough understanding
of internal moisture transfer mechanisms are important to optimise both the quality of the product and the economics of the
process. From a transport phenomena point of view, bread baking has been considered as a simultaneous heat and mass transfer
problem in a porous medium. Nevertheless, most efforts previously made have avoided modelling the phenomenon occurring in
the microscale, although the mechanism occurs primarily in the microscale. In this work heat and moisture transfer models
were developed to accomplish the mechanisms included, both in the microscale and the macroscale by means of Boltzmann’s equation.
Modelling and predictions of moisture transfer, heat transfer, modelling of effective moisture diffusivity, thermal conductivity
and diffusivity have been investigated in this work. The microstructure in the dough samples was obtained using micro-computer
tomography images from the samples prior to baking. The models were quantified and validated with measurements from the literature
in order to assess the predictive models. The simulated crust development has shown a crust thickness of 0.8 cm, which is
slightly higher than similar experimental results in which a dehydrated thickness of 0.5–0.6 cm was reported. The crust over-estimation
in this work fits to the overheating occurring in the model. Additionally, investigations were made on the influence of different
porosities (11–16%) of the bread; the boundary layer temperature at a porosity of 11% was reached after 25 min and after 17.5
min at a porosity of 16%. Therewith, the results showed that, with increasing porosity, the heat transfer rate towards the
centre was higher, which matches the knowledge of experienced bakers. |
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