Which Leafy Greens Should be Refrigerated to Prevent E. coli Contamination?

First it was butter, then ketchup and now it’s leafy greens… Should they be refrigerated or not?

After several recent outbreaks of foodborne illness related to lettuce, researchers decided to see how susceptible other greens are to harmful bacteria.

In a new study, they looked at the effect of E. coli contamination on romaine lettuce, green-leaf lettuce, spinach, kale and collards.

Whole leaves from each of the vegetables were infected and then stored at refrigerator temperature, room temperature and 98.6°F.

The results, according to the lead author, “At room temperature or higher, E. coli grows very fast on lettuce, but if lettuce is refrigerated at 39° F, we see a sharp decline in the E. coli population.

However, the opposite was true with kale and collards.

On these veggies, E. coli grew slower in warmer temps, and while it survived longer under refrigeration, kale and collards are typically cooked, which kills the bacteria.

The researchers also found juice from spinach, kale and collards had antimicrobial properties that protect against E. coli.

The authors say these findings shouldn’t stop you from eating fresh fruits and vegetables, but highlight the importance of washing your lettuce thoroughly and storing it in the refrigerator.