Scientists reveal best way to avoid E. coli poisoning from lettuce

By Sharin Hussain via SWNS

Lettuce should be kept in the fridge if you want to avoid a nasty bout of E. coli poisoning, scientists advise.

But with other greens such as kale, keeping them out of the fridge is better to avoid becoming ill from the bug.

Green vegetables are important sources of dietary fiber and nutrients, but they can harbor harmful pathogens.

The study, published in the journal, Food Microbiology, examined five leafy greens – romaine lettuce, green-leaf lettuce, spinach, kale, and collards.

The researchers infected whole leaves from each of the five vegetables with E. coli and observed what happened after storage at 4° C, 20° C, and 37° C.

They found that the combination of temperature and the leaf texture determined how the vegetable performed.

Lead author Dr. Mengyi Dong at University of Illinois Urbana-Champaign said: “We are seeing a lot of outbreaks on lettuce, but not so much on kale and other brassica vegetables. We wanted to learn more about the susceptibility of different leafy greens.

“At room temperature or higher, E. coli grows very fast on lettuce, but if lettuce is refrigerated at 4° C, we see a sharp decline in the E. coli population.

“However, for waxy greens like kale and collard, we get the opposite results. On these vegetables, E. coli grows slower under warmer temperatures, but if it is already present, it can survive longer under refrigeration.”

Kale and collard are usually cooked and overall less susceptible to E. coli contamination than lettuce, a vegetable that is eaten uncooked.

Washing your lettuce does help but doesn’t remove all the bacteria because of their tight attachment to the leaf.

Dr. Dong added: “Whole leaves and freshly cut leaves present different situations. When the leaf is cut, it releases vegetable juice, which contains nutrients that stimulate bacterial growth.”

The study found that spinach, kale, and collard juice exhibited antimicrobial properties that protect against E. coli.

The researchers also suggest that a spray could be created to control foodborne pathogen contamination at pre-harvest and post-harvest stages.

Co-author Professor Pratik Banerjee said: “We can’t completely avoid pathogens in food. Vegetables are grown in soil, not in a sterile environment, and they will be exposed to bacteria.

“It’s a complex problem to solve, but we can embrace best practices in the food industry and food supply chain.

“There's a lot of interest from the research community and federal agencies to address these issues, and the USDA imposes high standards for food production, so overall the U.S. food supply is quite safe.”

The researchers say they do not want to discourage people from eating fresh fruit and vegetables as they are part of a healthy diet.

They recommend you follow food safety guidelines, wash your lettuce thoroughly, store it in the refrigerator, and pay attention to any food safety recalls in your area.