Reducing Salmonella contamination in mangoes

Fresh produce almost needs to come with a food safety warning. Any foodborne pathogens picked up during growing, picking, packaging and transporting fresh produce cannot easily be eliminated by a traditional kill step such as cooking because the produce is eaten raw.

Contaminated rockmelons, papayas, cucumbers and fenugreek sprouts are just some of the fresh produce that have resulted in fatalities in recent times.

Salmonella is one of the pathogens that cause concern when contaminating fresh produce. The US Centers for Disease Control and Prevention estimates that in the US each year, Salmonella leads to approximately 1.2 million cases of Salmonellosis, around 23,000 hospitalisations and 450 deaths.

Mangos contaminated with Salmonella caused a multistate outbreak of disease in the US in 2012. The bacteria can get into the water used to wash the fruit in processing plants and so contaminate the fruit.

In mango processing plants, the wash water is housed in gigantic tanks, and once the water is contaminated, the bacteria are able to attach to the fruit’s skin and then enter the fruit’s pulp. Once bacteria make their way into the fruit, no amount of washing can remove them. With so many mangoes washed at once, the number of contaminated mangoes can be numerous, potentially causing many cases of Salmonellosis.

A University of Connecticut lab recently processed 4000 mangoes and water samples to test the efficacy of three disinfectants commonly used by the mango industry to avoid contamination. The results surprised the researchers — chlorine was found to be particularly effective. Not only did chlorine clean the wash water, it also helped prevent cross-contamination by cleaning the mangoes themselves.

This result was surprising because chlorine is not usually very effective in the wash step for most produce. For one reason or another, from lettuce, to tomatoes to apples, chlorine simply doesn’t reliably kill Salmonella.

“When I saw the results, I didn’t believe it. So we re-ran the test 10 times,” said Mary Anne Amalaradjou, assistant professor in the Department of Animal Science.

What is noteworthy is that not all produce responds the same way to the same disinfectant.