Pre-heated blades for harvesting baby-leaves reduce the risk of Escherichia coli internalization in leaves

Background. Pathogenic enterobacteria can travel through the plant vascular bundles, by penetrating from cuts and persist into ready-to-eat leafy greens. As the cutting site is the main point of entrance and uptake, we tested how different cutting strategies can reduce bacterial internalization in leaves. Horizontal cuts at the base of the leaves were performed with two different types of tools, the first with a scalpel (by pulling the blade) and the second with a scissor-action that has blades that cuts by gliding against a thicker blade. Scissor-action generally makes closer border cuts. Blades of both types of tools have worked at 25 °C and 200 °C. The goal was to study how these different types of cuts and temperatures affected bacterial uptake in leaves. Experiments were repeated on different plant genotypes and at different wilting stages. Results. Our finding showed that cutting baby-leaves with a scissor at 200 °C significantly reduced the bacterial uptake when compared with the not heated (which simulates a mechanized lettuce harvester). The most effective cutting treatments to reduce bacterial uptake were in order: scissor 200 °C > scissor 25 °C > scalpel 200 °C > scalpel 25 °C. The scissor heated at 200 °C was also preventing bacterial uptake on wilted baby-leaves. Conclusions. This finding could provide further contribution in terms of safety during harvest and suggest that a pre-heated blade supports safety during harvest of leafy greens.