In news that will probably send you straight to the vegetable crisper, scientists have discovered that bagged salad leaves are the perfect breeding ground for dangerous bacteria to frolic in.

And not just any bacteria; salmonella is apparently having an absolute field day in your ready-washed rocket. 

“Salad leaves are cut during harvesting and we found that even microlitres of the juices which leach from the cut ends of the leaves enabled salmonella to grow in water, even when it was refrigerated,” Dr Primrose Freestone, a lead scientist at the University of Leicester’s Department of Infection, Immunity and Inflammation, said.

“These juices also helped the salmonella to attach itself to the salad leaves so strongly that vigorous washing could not remove the bacteria, and even enabled the pathogen to attach to the salad bag container.”

The study found that bacteria growth was boosted more than 2,400 fold thanks to liquid seeping from the leaves of cos, baby green oak, red romaine lettuce, spinach and red chard. 

“This strongly emphasises the need for salad leaf growers to maintain high food safety standards as even a few salmonella cells in a salad bag at the time of purchase could become many thousands by the time a bag of salad leaves reaches its use-by date, even if kept refrigerated,” Dr Freestone continued.

“Even small traces of juices released from damaged leaves can make the pathogen grow better and become more able to cause disease.”


If you really, really can’t do without your bag of ready-to-go salad, researchers recommend tucking in as soon as possible; once the bag is opened, bacteria growth is boosted even further.

Interesting how you don’t hear about people getting food poisoning from chocolate, hey?

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