Juices from damaged salad leaves “massively stimulate” Salmonella growth, according to a new study from the University of Leicester.
Researchers found that just a small amount of damage to salad leaves can increase the risk of Salmonella, and said results “strongly emphasises” the need for salad growers to maintain high food safety standards. The salad juices also increased the Salmonella pathogen’s capacity to form a strong and wash-resistant attachment to salad leaves, results found.
“Salad leaves are cut during harvesting and we found that even microlitres of the juices (less than 1/200th of a teaspoon) which leach from the cut-ends of the leaves enabled Salmonella to grow in water, even when it was refrigerated,” said project leader Dr Primrose Freestone.
“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.
'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. Even small traces of juices released from damaged leaves can make the pathogen grow better and become more able to cause disease.”
Researchers said the study also serves as a reminder to consume bagged salad as soon as possible after opening. “We found that once opened, the bacteria naturally present on the leaves also grew much faster even when kept cold in the fridge,” she said.
“This research did not look for evidence of Salmonella in bagged salads. Instead, it examined how Salmonella grows on salad leaves when they are damaged.'
Up until now, there have been few studies looking at the behaviour of Salmonella once leaves have been bagged, the researchers said.
Research published recently by the Food Standards Agency said that of the 500,000 cases of food poisoning in the UK every year, some 48,000 were from fresh produce: vegetables, fruit, nuts and sprouting seeds.
