Cut leaves in bagged salads help Salmonella grow

That past-its-prime bag of spinach buried in the back of your fridge should probably hit the compost heap instead of your dinner plate. The watery gunk that accumulates at the bottom of bagged salad mix is the perfect breeding ground for Salmonella bacteria that could make people sick, researchers report November 18 in Applied and Environmental Microbiology.

The culprit? The juice that oozes out of cut or damaged leaves. After five days in the fridge, small amounts of plant juice sped up Salmonella growth. The bacteria grew avidly on the bag and stuck persistently to the salad leaves, so much so that washing didn’t remove the microbes.

Salmonella’s success inside bagged salads means it’s important for producers to avoid bacterial contamination from the get-go — and for consumers to eat those greens before they get soggy. Popeye would approve. 


G. Koukkidis et al. Salad leaf juices enhance Salmonella growth, fresh produce colonisation, and virulence. Applied and Environmental Microbiology. November 18, 2016. doi: 10.1128/AEM.02416-16.

Further Reading

J. Raloff. Wash your veggies! Science News Online, June 11, 2008.


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