Pore-scale modeling of antimicrobial gas flow in a bed of low-moisture food

Pathogen contamination on the surface of low-moisture foods such as dried basil leaves can lead to foodborne illnesses. Antimicrobial gas treatment is a promising non-thermal intervention for pathogen reduction in low-moisture foods. The passage of antimicrobial gases through the inter-leaf pore channels of the basil bed can enhance food safety by targeting pathogens on the leaf surfaces. In this study, a novel procedure is introduced to investigate the mechanistic aspects of antimicrobial gas flow through porous channels in basil bed. X-ray micro-computed tomography, image processing, and pore network modeling (PNM) were used to characterize the microstructure of the basil bed. 3D and 2D CFD pore-scale models, along with a 3D PNM were developed to simulate antimicrobial gas transport through the bed's porous channels. The results indicated that the bed has a total porosity of 0.654. Only 0.6 % of total pores are closed and blind, which makes them inaccessible to the antimicrobial gas. The average pore body radius, throat bond radius, and pore coordination number are 436.7 μm, 191.4 μm, and 8.2, respectively. The antimicrobial gas pressure gradually decreases along the direction of gas flow, whereas its velocity exhibits fluctuations. The bed permeability is of the order of 10⁻⁹ m². The permeability in the radial direction is 64 % higher than in the axial direction, based on the PNM results. It was also revealed that various interconnected pore channels pass antimicrobial gas at different flow rates, which is expected to affect the effectiveness of pathogen destruction. Results showed that the flow direction needs to be changed dynamically to ensure the antimicrobial gas reaches a greater number of blind pores.