Steam effectively rids melons of bacteria
Steam can more effectively combat E. coli, Salmonella, and Listeria on cantaloupes than traditional removal methods. That’s the finding of an Agricultural Research Service (ARS) scientist in Pennsylvania.
Dike Ukuku and his colleagues at the ARS Food Safety and Intervention Technologies Unit in Wyndmoor has demonstrated that a relatively inexpensive steam cleaner designed to remove wallpaper and clean outdoor grills can rid cantaloupes of E. coli, Salmonella, and Listeria more effectively than existing washes and chlorine treatments.
The ARS study involved submerging cantaloupes in a bath inoculated with E. coli, Salmonella and Listeria strains. After drying and refrigeration at 41 °F for 7 days, the cantaloupes were cleaned with a commercially available power steamer. The spray nozzle was swept across the fruit for 3 minutes. They placed the nozzle 3 inches from the cantaloupe, a distance that produced 154 °F steam at the point of contact. The technique produced sufficient heat to kill surface pathogens but not enough heat to damage the fruits. They used a 915 Wagner Power Steamer, but any steamer generating the same heat would likely produce similar results.
Some cantaloupe were cut up immediately after being steamed. Others were stored for 7 days at 41 °F and then cut up.
Pathogen levels on the surfaces of the steam-treated melons were generally 1,000 times lower than those on untreated melons. Pathogens on cut-up pieces of the cantaloupes were reduced beyond detection. Pathogen levels on steam-treated cantaloupes were about 100 times lower than those found on cantaloupes sanitized with chlorine.
The cut-up melon pieces showed no undue softening, discoloration, or unwanted odors, either right after the treatment or up to 7 days later. The researchers refrigerated treated melons for 29 days to check for abnormal ripening, decay and defects but found none.
Processors and distributors could apply steam when cantaloupes are put into washers or as they are moved on conveyor belts during processing, Ukuku said. The technique also may effectively sanitize watermelons, honeydews, cucumbers and baby carrots.
The new technology could reduce the number of foodborne disease outbreaks from contaminated produce, which annually cause nearly one million illnesses and more than 100 deaths.
The research appeared in the International Journal of Food Microbiology in 2016.
— Dennis O’Brien, Agriculture Research Service, U.S. Department of Agriculture
