Pre-prepared salads sold in supermarkets may pose serious health risks.  Researchers from University of Leicester said that they have found evidence that the environment inside a salad bag offers an ideal breeding ground for salmonella.  Salmonella poisoning is the second most common intestinal infection in the United States. 

The Researchers Mimicked The Salad Bag Environment And Found Salmonella Growth

The authors of the study - Giannis Koukkidis, Richard Haigh, Natalie Allcock, Suzanne Jordan and Primrose Freestone - grew salmonella in salad juice and leaves at different temperatures to see what happened.  They mimicked the grocery salad bag environment.  They showed movement of individual salmonella bacteria more than doubled in such an environment.  After being refrigerated for about five days, 100 salmonella bacteria had multiplied to about 100,000.

"We found that juices released from the cut-ends of the salad leaves enabled the Salmonella to grow in water, even when it was refrigerated - this was a surprise as Salmonella has a temperature preference of 37 C.  Collectively, this study shows that exposure to salad leaf juice may contribute to the persistence of Salmonella on salad leaves, and strongly emphasizes the importance of ensuring the microbiological safety of fresh produce," the researchers said.

Salmonella Attached To The Salad Leaves Strongly

Freestone, one of the authors of the study said: "Salad juice exposure also helped the Salmonella cells to attach to the salad leaves so strongly that washing could not remove them. Collectively, this study shows that exposure to even traces of salad leaf juice may contribute to the persistence of Salmonella on salad leaves as well as priming it for establishing an infection in the consumer."

Experts say that in order to avoid poisoning, common precautions, such as washing your hands and food thoroughly before preparation, and making sure use-by dates are followed, should be adhered.