According to American researchers who studied the best storage methods to avoid E. coli contamination with green leafy vegetables, salad should be put in the refrigerator to avoid food poisoning.
- Green leafy vegetables – such as lettuce and cabbage – are often implicated in E. Coli bacteria contamination.
- Researchers found that the bacteria grew less on lettuce if it was refrigerated to 4 degrees.
- Waxy greens like kale and collard greens, on the other hand, are better protected by warmer temperatures.
The bacteria Escherichia coli (E. coli) is responsible for many food poisonings. One of its favorite shelters is green leafy vegetables like salad. Researchers from the University of Illinois Urbana-Champaign (USA) wanted to identify the factors that make them vectors of the pathogenic agent or not.
E.Coli: put the salad in the fridge to reduce contamination
“We see a lot of outbreaks on lettuce, but not so much on kale and other brassica vegetables. We wanted to know more about the susceptibility of different leafy vegetables.”explains lead author Mengyi Dong in a communicated.
The researchers thus infected whole leaves of five vegetables (romaine lettuce, leaf lettuce, spinach, kale and collard greens) with the bacteria E. coli O157: H7. The food was then stored at 4°C (fridge temperature), 20°C and 37°C. The team then noticed that sensitivity to the pathogen depended on a combination of several elements: temperature and leaf surface properties.
“At room temperature or above, E. coli grows very quickly on lettuce, but if it is refrigerated to 4°C, we see a sharp drop in the E. coli population. However, for green leafy vegetables “Waxy vegetables like kale and collard greens, we get opposite results. On these vegetables, E. coli grows more slowly in warmer temperatures, but if it’s already present, it can survive longer under refrigeration.”explains the expert.
Despite this, both types of cabbage are overall less susceptible to E. coli contamination than lettuce. In addition, the latter are generally cooked – which kills or inactivates the bacteria – while salad is eaten raw. Mengyi Dong recommends putting salad in the fridge to reduce the risk of infection. Furthermore, he adds that rinsing lettuce is useful, but it does not eliminate all the bacteria present on the leaves.
Food poisoning: you should not give up fruits and vegetables
And what happens if we cut out these foods? Researchers have looked into the question. “Whole leaves and freshly cut leaves present different situations. When cut, it releases vegetable juice, which contains nutrients that stimulate bacterial growth”, warns the main author. However, the work, published in the next issue of Food Microbiology, reveal that spinach, kale or green juices also had antimicrobial properties that protect against E. coli.
Additionally, the scientists emphasize that their study is not intended to discourage eating fresh fruits and vegetables, as they are an essential component of a healthy diet and good health. “Simply follow food safety guidelines, wash your lettuce thoroughly, store it in the refrigerator, and watch out for any food safety recalls in your area.”they conclude.
