Not all fruits are created equal. And that's proving to be a point of contention in the wake of the outbreak of listeriosis linked to cantaloupe from Jensen Farms in Colorado. Fifteen people have died from listeriosis, an infection brought on by the listeria bacteria.
Few outbreaks have been linked to produce. Hot dogs, deli meats and soft cheese are the usual culprits. The meat industry did a major revamp of its methods, and now outbreaks are down, but they seem to be climbing in produce.
It's well-known that rough-skinned cantaloupes "are inherently riskier" than a melon like a honeydew that has a smooth skin, says Jim Prevor, whose online column, The Perishable Pundit, is widely read in the industry.
That's probably something of a surprise to most Americans, who generally see cantaloupes as the quintessential healthy breakfast fruit.
"There are lots of places for bacteria to bind on the surface. It's like a mountain range under the microscope," says Doug Powell, a professor of food safety at Kansas State University in Manhattan. But there's not much consumers can do. If the listeria is on the rind, when you cut it open, "it's going to cross-contaminate."
Cantaloupe growers, packers and sellers are not unanimous in deciding the best way to reduce the risk of listeria contamination on cantaloupes.
About 85% of cantaloupes grown in the USA come from California and Arizona's arid high deserts, where they're watered using drip irrigation, which keeps them relatively clean. That means they don't need to be washed before being shipped, which experts say cuts down on the possibility of one contaminated melon tainting a whole vat of them as they're being washed.
The other 15% are grown in the South, where rain is more likely to splatter them with mud and make them impossible to sell without washing. In the winter season, November through April, cantaloupes come from Mexico and Central America, where they're also more likely to get wet.
Bringing cantaloupes into a packing shed, where they touch surfaces that have touched other melons and may be dunked in a tank of water to clean them, "has every opportunity to reduce risk but equal or greater opportunity to contaminate," says Trevor Suslow, a food-safety expert at the University of California-Davis who has done extensive research on cantaloupes.
Washing "is certainly a good practice, but you need to do that in an area that you won't introduce contamination" into other melons.
Listeria is an especially problematic bacteria because it exists in the environment, in dirt and animals; once a colony starts growing on processing equipment, it can form biofilms that are difficult to remove. "They hide in the nooks and crannies," Suslow says. "You've got to go in with steam and stronger chemicals" to get rid of them.
Washing may not be the only answer.
Craig Wilson, Costco's food-safety director, says his company does require sellers to wash their cantaloupes, but what he's moving toward "in the very near future" is a test-and-hold program. Growers and packers who want to sell him melons will need to test them for a broad range of potential pathogens such as "E. coli, salmonella, listeria" and not ship to him until the results come back negative, a process that takes eight to 48 hours.
"This not a bad industry, it's a good industry," Wilson says. "The cantaloupe folks are great, we just need to work together to get beyond this."
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