# Effect of bread microstructure on internal liquid penetration using the lattice Boltzmann method combined with X-ray micro-computed tomography

## TL;DR

This study uses advanced imaging and simulation to show how bread's internal structure affects liquid penetration, finding that connectivity and pore size matter more than porosity alone.

## Contribution

The paper introduces a novel combination of X-ray micro-tomography and lattice Boltzmann methods to analyze bread microstructure's impact on fluid flow.

## Key findings

- Porosity alone is insufficient to predict permeability in bread microstructures.
- Higher connectivity along the main flow direction enhances permeability.
- Small broken holes in the pore structure act as bottlenecks, restricting fluid flow.

## Abstract

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 (D50) is identified as a representative measure of flow capacity. In contrast, tortuosity and the number of junctions show only negligible correlations with permeability.

Graphical abstract Image 1

•X-ray micro-tomography was utilized to analyze the microstructure of bread.•An enhanced lattice Boltzmann method was employed to capture pore-scale liquid penetration in bread.•Key pore structural properties were quantified and related to permeability prediction.•(Effective) porosity alone is inadequate for accurate permeability prediction.•Topological characteristics strongly influence fluid flow in bread.

X-ray micro-tomography was utilized to analyze the microstructure of bread.

An enhanced lattice Boltzmann method was employed to capture pore-scale liquid penetration in bread.

Key pore structural properties were quantified and related to permeability prediction.

(Effective) porosity alone is inadequate for accurate permeability prediction.

Topological characteristics strongly influence fluid flow in bread.