Effect of bread microstructure on internal liquid penetration using the lattice Boltzmann method combined with X-ray...

Understanding the influence of food matrices on the penetration process is essential for optimizing filling and spreading techniques in food processing. In this study, an enhanced lattice Boltzmann method coupled with X-ray micro-computed tomography scanning is used to simulate fluid dynamics within the real microstructure of bread at the pore scale. The influence of micro-structural characteristics of bread (porosity, connectivity, pore size distribution, tortuosity) on liquid penetration is investigated. The numerical model is validated using three benchmarks to ensure its applicability and assess accuracy for heterogeneous porous media. The results indicate that relying solely on porosity or effective porosity to predict permeability is not sufficient, as no simple correlation is observed between permeability and porosity. Investigating the internal flow dynamics suggests that higher connectivity, particularly along the main flow direction, is identified as the dominant factor controlling permeability by offering further paths for fluid movement. In addition, details of the pore structure also play an important role, especially when many small broken holes are observed. Those constitute bottlenecks that restrict fluid flow and significantly influence the global flow features. The median pore size ( $D_{50}$ ) is identified as a representative measure of flow capacity. In contrast, tortuosity and the number of junctions show only negligible correlations with permeability.