Unveiling safer greens. How temperature & leaf type affect E. coli risks

A study explored how leaves from various vegetables responded to E. coli bacteria when stored at temperatures of 39°F, 68°F, and 99°F. The findings suggest that factors like temperature and the leaf's surface characteristics, including roughness and a natural waxy layer, impact their susceptibility to contamination.

Generally, kale and cabbage are less likely to be contaminated by E. coli than lettuce. Even when cabbage and kale are contaminated, the bacteria tend to be removed during typical cooking processes.

Lettuce, often eaten raw, presents a different issue. While washing can reduce bacterial presence, it doesn’t always eliminate it.

"At room temperature or above, E. coli rapidly proliferates on lettuce. However, storing it at 39°F significantly curbs bacterial growth. Waxy vegetables like kale or cabbage behave differently; E. coli grows more slowly at higher temperatures but can survive longer in colder conditions," explains Mengyi Dong, the study's lead researcher.

Further experiments showed differences in bacterial behaviours between chopped and whole leaves. "Chopped leaves release a nutrient-rich juice, creating an environment conducive to bacterial growth," says Mengyi Dong.

The research team discovered that spinach, kale, and cabbage juice have antibacterial properties effective against E. coli. Additionally, applying a lysate from kale and cabbage to lettuce leaves can act as a natural antibacterial agent.

These findings could introduce new strategies for mitigating food contamination by pathogens.