Mechanistic understanding of temperature-driven water and bacterial infiltration during hydrocooling of fresh produce

• We developed a 3D porous media model on reconstructed tomato from MRI.
• Cooling rate and temperature gradient strongly influences pathogen internalization.
• SEM and μCT of stem scar show it is extremely porous and ideal for internalization.

Freshly harvested fruits and vegetables (produce) are chilled to extend their shelf life but the chilling process increases opportunities for contamination by pathogenic bacteria carried by water through openings such as stem scars. Using tomato as a representative system, a 3D porous medium transport model is developed. The model simulates the transport of water vapor, liquid water, bacteria, and energy in light of convection–diffusion processes driven by pressure gradients from condensation inside as well as by water concentration gradients between the cooling water and that in the tomato. Results show that increasing the rate of cooling (i.e., creating a higher temperature difference) increases the rate of infiltration due to higher-pressure gradients. A higher temperature differential drives bacteria further into the tomato. A less hydrated tomato will incur deeper and more extensive infiltration. Size, permeability, and diffusivity play a less significant role. The novel mechanistic understanding our study provides should aid in designing safer hydrocooling processes.