A study finds that bagged salad can encourage the growth of various food-poisoning bugs like Salmonella. The last thing one would expect when purchasing salad from the local supermarket is a full-blown Salmonella infestation.
A group of scientists from the University of Leicester found that a combination of moisture and leaking nutrients from chopped leaves makes for the best breeding ground for bacteria. Furthermore, the cold temperatures do little good in preventing bacteria growth. Hence, not even the fridge can stop a Salmonella infestation. However, bacteria colonies start to develop after several days. Hence, the scientists advise to eat bagged salad on the same day they buy it.
Events Leading Up to the Research
Back in 2011, a Salmonella infestation affected more than 2,000 people across Europe. Surprisingly, the source was traced back to bean sprouts. In 2016, two British people died as consequence of consuming infected rocket leaves.
As a result, scientists wanted to know more about the main cause of these serious outbreaks rampaging through Europe. They concluded that minerals, proteins, and sugars leak from the cut leaves and mix with the water in the bag. Furthermore, moisture present on the inside of the salad bags contributes to the rapid development of harmful bacteria. As a consequence, the harmful pathogens thrive on the highly nutritious environment.
“That’s a reasonable amount of nutrients if you’re a bacterium”, says Dr. Primrose Freestone, one of the researchers.
The Research Team’s Highlights
The study shows that an initial population of 100 Salmonella bacteria increases up to 100,000 individuals in five days’ time. “That’s more than an infectious dose”, says Dr. Primrose Freestone. Hence, it is safe to assume that a Salmonella infestation of such magnitude can only be fatal.
Furthermore, the study determined that while E. coli thrives on rocket leaves, Salmonella does especially well in bags which contain spinach. He warns that one could not simply wash off a bacteria colony as easily as it seems. Mainly thanks to the overwhelming population of harmful pathogens.
However, she does not imply that bagged salad should be avoided altogether. It is better to consume it on the same day one buys it. Furthermore, “buy the bag with the best sell-by date, avoid lots of mushed leaves and if it’s inflated, then don’t use it”, says Dr. Freestone.
The study also suggests that bacteria can become more dangerous in a sealed environment, such as plastic bags used for storing salad. The genetic analysis of the Salmonella shows that the individuals suffer multiple mutations. As a result, they gain the ability to infect humans more easily.
“Avoiding fresh produce is not a solution”, says Dr. Kimon Karatzas of Reading University. However, he strongly suggests that people should look for uncut fresh produce over chopped, to prevent a Salmonella infestation.
Needless to say that consumers should thoroughly wash each product before eating it. As one more piece of advice, Dr. Karatzas recommends keeping fresh produce in the refrigerator to prevent bacteria growth.
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