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Optimize melon safety with steam.

A relatively inexpensive commercial steam cleaner, intended to remove wallpaper and clean outdoor grills, kitchen counters and other household surfaces, can rid cantaloupes and other produce, such as watermelons, honeydew melons, cucumbers and baby carrots, of Escherichia coli, Salmonella and Listeria more effectively than existing washes and chlorine treatments.

The technique could be used to sanitize produce without significantly adding to food processing costs. Processors and distributors could apply the steam when cantaloupes are put into washers, or as they pass along on conveyor belts during processing.

The use of steam could reduce the number of cases of foodborne outbreaks from contaminated produce, which each year causes an estimated 1.2 million illnesses, 7,100 hospitalizations and 134 deaths. The illnesses also generate $1.4 billion in illness-related costs, according to the US Centers for Disease Control and Prevention.

USDA-ARS researchers submersed 24 cantaloupes in a bath inoculated with E. coli, Salmonella and Listeria strains, then dried and refrigerated them at 41 F for seven days. They then used a commercially available power steamer to steam-clean the cantaloupes by sweeping the spray nozzle 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. That temperature was hot enough to kill surface pathogens but not damage the fruit. Some of the cantaloupes were cut up immediately after being steamed. Others were stored for seven days at 41 F and then cut up.

The results showed that the steam treatment was effective at killing the pathogens. Pathogen levels were generally 1,000 times lower on the surfaces of steam-treated melons, a 99.9% reduction, and were undetectable on the cut-up pieces. Surface pathogen levels 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 seven days afterwards. The researchers refrigerated treated melons for 29 days to check for abnormal ripening, decay and defects, but found none.

Further information. Dike O. Ukuku, USDA-ARS Food Safety and Intervention Technologies Research, Eastern Regional Research Center, Room 3024B, 600 E. Mermaid Lane, Wyndmoor, PA 19038; phone: 215-233-6427; fax: 215-233-6406; email:

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Author:Ukuku, Dike O.
Publication:Emerging Food R&D Report
Date:Apr 1, 2017
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