How bacteria infiltrate edible leafy greens
How bacteria infiltrate edible leafy greens lead image
As leafy greens travel from field to fork, they can be infected with bacteria in a number of different ways. Mohsen Ranjbaran and Ashim K. Datta studied one possible mechanism for bacteria to transport from the surface of leaves into their internal tissue – through the evaporation of bacteria-containing droplets on leaf surfaces.
The researchers found that internal flows within water droplets help transport bacteria from the droplet onto the leaf surface. As the droplet evaporates, bacteria can infiltrate into the leaf via microstructures such as pores and grooves. The size and spacing of the structures, as well as the hydrophobicity of the leaf, all play a role in how much bacteria is transferred and how it is distributed over the surface.
“Once the bacteria are inside the leaf tissue, the consumer can never kill them or remove them by surface washing, unless they cook the leaves,” said Ranjbaran. “Since a lot of people consume leafy greens raw, they will be at risk of bacterial infections.”
To better represent a wide variety of plants, Ranjbaran and Datta compared results from a spinach leaf and an artificial polymer leaf. They fabricated the artificial leaf with different microstructure sizes and spacings, and deposited a coating to adjust its hydrophobicity. They then placed water contaminated with bacterial cells at the surface of each leaf.
“If this contaminated water is not washed right away, then it evaporates in a few minutes and the microbes are transported into the leaf micropores,” Ranjbaran said.
Evaporation-driven bacterial transport is just one pathway that promotes bacterial infiltration into leaves. The authors note that a comprehensive understanding of all possible pathways is necessary to design and optimize food safety protocols.
Source: “Retention and infiltration of bacteria on a plant leaf driven by surface water evaporation,” by Mohsen Ranjbaran and Ashim K. Datta, Physics of Fluids (2019). The article can be accessed at https://doi.org/10.1063/1.5126127 .
