The disgusting reason you should be wary about tucking into bags of ready-washed salad leaves
Bags of washed salad leaves are breeding grounds for dangerous bacteria, including salmonella, according to new research.
Scientists revealed that liquid which seeps from damaged leaves can boost the growth of bacteria in the bag by more than 2,400 fold before they are tossed onto your plate.
The research found that juice from the leaves increased salmonella growth by 110pc when mixed with the moisture already present in the bag.
The research was focused on the way in which food bug salmonella thrives on broken and damaged leaves and analysed salads containing cos, baby green oak, red romaine lettuce, spinach and red chard, which make regular appearances in ready-made salads in the UK and Ireland.
Experts at the University of Leicester in the UK advised consumers to avoid pre-washed salads if at all possible, and if purchased to keep it chilled at all times.
Lead scientist Dr Primrose Freestone, from the University of Leicester's Department of Infection, Immunity and Inflammation, said: "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.
"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."
Those who do purchase ready-washed salad are advised to consume their vegetables very soon after purchase, as the temperature of the fridge does little to halt the spread of the bacteria.
"We found that once opened, the bacteria naturally present on the leaves also grew much faster even when kept cold in the fridge," Dr Freestone added.