With several handling steps from when mangoes first enter the packinghouse until they reach the retailer, Danyluk - a University of Florida associate professor of food science based in Lake Alfred - wants to significantly reduce pathogen risks with each process.
"Currently, no one process in a packinghouse is going to give us the sort of 'kill step' we see in manufactured foods," Danyluk said. "Instead, we're going to need to focus on hurdle technologies, where every subsequent step prevents contamination. To evaluate the safety of a product, you really need to look at every step in packing and shipping."
Leonardo Ortega, director of research for the Orlando, Fla.-based National Mango Board, said Danyluk's project is important to the industry because scientific literature carries scant mango-specific food safety information.
"She's checking different parts of the mango supply chain to see how pathogens behave on the surface of mangoes and how they behave in the cooling rooms and when the industry stores mangoes," Ortega said. "Then we'll know what happens with these pathogens, and it will be good for us."
The National Mango Board has worked closely in the past with University of Florida researchers, and Ortega said he was glad to continue the collaborative effort with Danyluk and her colleagues on this project.
"CPS and the researchers have identified the real needs of the mango industry and that's to develop the best practices for food safety," he said.
Danyluk also praised the National Mango Board and its members for helping make her research meaningful for the industry.
"Their input, from the initial proposal stage through the revision of the submission and into all the experimental parameters, has been essential," she said. "We want our experiments to be impactful and without industry input to make sure we're replicating what the industry does, I'm not sure how impactful we'd be. The National Mango Board has also been very helpful in helping us source the different varieties of mangoes from around the world."
The first step of the research project involved looking at the fate of the pathogen, Salmonella enterica, inoculated on the surface of mangoes held at 54 degrees Fahrenheit, 68F and 86F for up to 28 days. The fruit held at 86F didn't make it past seven to 14 days before the quality had deteriorated too much.
The temperatures were selected to represent the ranges from when fruit is unloaded at a packinghouse to the highest recommended level to prevent poor ripening and flavor.
The trial also examined several mango varieties, including Kent, Tommy Atkins, and Ataulfo or Honey, to determine whether there were varietal differences.
"Boy, was I surprised at the difference between what I pictured in my mind when someone says a mango and some of the varieties we've worked with," she said. "Seeing those differences in varieties, I absolutely expect to see differences between some of the varieties in some of the studies we're doing."
In previous work, Danyluk had examined various pathogen behaviors on fresh-cut mangoes, but it did not include Listeria. So the researchers spent time looking at how L. monocytogenes behaved compared to Salmonella and Shiga toxin-producing E. coli.
Mangoes pose additional challenges since they are not simply washed and packed. Instead, fruit destined for many export countries also must undergo a subsequent insect quarantine treatment that involves hot water immersion, vapor heat or forced hot air.
The second part of the research will focus on the mitigation strategy for fruit before the quarantine treatment. It will involve a spray wash and brushes to remove soil, latex and other materials adhering to the mangoes' surface.
Danyluk based the strategy on work conducted by UF colleague Dr. Keith Schneider on fresh-market tomatoes. He found a spray wash and brushes were very effective and easier for the packer to manage in terms of sanitizers compared to recirculating dump tanks.
Probably the most important reason for emphasizing fruit cleanliness, Danyluk said, is "pathogens can internalize during cooling following (quarantine) treatment. And the best way to prevent this internalization is to prevent pathogens from being present when the mangoes are treated."
She said her project also complements previous CPS-funded research titled, "Impact of wash water on Salmonella enterica transfer and survival in mango packing facility water tank operations," and led by Dr.
Mary Anne Amalaradjou
with the University of Connecticut.
"Mary Anne's work and our work here can be combined to provide a full picture of how to ensure the safety of mangoes," Danyluk said.