The convenience of bagged, prewashed salad can be a big plus when it comes to getting ample servings of vegetables every day. Just when you thought you had this part figured out, in come the research party-poopers (in the best way, of course) to rain on your easy greens.

Simply put, be careful. Even though most bagged salad is washed multiple times and then carefully sealed, the potential for foodborne illness still exists, according to a study published in Applied and Environmental Microbiology (2017; 83 [1], e02416).

Scientists found that during 5 days of refrigeration, traces of nutrient-rich juices released from crushed greens in the bags nourished Salmonella bacteria and multiplied its growth by as much as 280 times, when compared with sterile water. The juice not only helped the bacteria to attach to leaves in the bag but supported bacterial growth on the plastic bag itself.

The authors offer the following best practices to ensure the safety of your salad:

  • Check and heed use-by dates.
  • Rinse and spin-dry thoroughly before eating.
  • Avoid purchasing bags that are puffy or swollen.
  • Forgo bags with crushed, mushy or slimy leaves.
  • Keep greens refrigerated.