Hot water immersion treatment for cantaloupes to enhance food safety has proven effective in the laboratory and could make the leap to commercial use, according to the U.S. Department of Agriculture.

Bassam Annous, research microbiologist with the Eastern Regional Research Center for the USDA’s Agricultural Research Service, Wyndmoor, Pa., said the department is working with industry on a hot water bath system for cantaloupe.

“Basically, I’m trying to develop it to be commercial-scale friendly so the industry would be willing to use based on the criteria of what they do,” he said Jan. 26

Annous said confidentiality agreements don’t allow him to discuss details of test runs by melon shippers, or the companies that are involved in the trials.

The process has gained interest recently, after 30 deaths were linked to listeria from cantaloupes grown in Colorado in 2011. At a Jan. 11 meeting sponsored by the Center for Produce Safety, food safety and California cantaloupe industry members discussed establishing a voluntary oversight organization similar to the California and Arizona Leafy Green Marketing Agreements. Growers established those groups after the 2006 E. coli outbreak linked to fresh spinach.

The hot water treatment is one possible reponse to the listeria outbreak, according to melon growers, who met Jan. 12 in connection to the Center for Produce Safety meeting.

Annous, hired by the USDA in 1998 to work on produce safety issues, developed the hot water system for cantaloupe about seven years ago after reports of foodborne illness outbreaks linked to the fruit in 2002 and 2003 spurred interest in the approach.

Annous said the process — which involves a hot water bath for three minutes at 168 degrees — has proven very effective in killing salmonella that was artificially inoculated on the surface of the cantaloupe by researchers.

“We saw really good kills, to almost non detectable levels of the pathogen after the treatment,” he said.

A rough estimate of the cost of the hot water treatment process developed several years ago put it at one or two cents per melon, he said.

More research will be done the hot water treatment’s effectiveness on listeria, Annous said.

The thick rind of the cantaloupe protects the flesh from damage during the hot water treatment, and Annous said there are indications the process actually benefits the shelf life of cantaloupe prepared for the fresh-cut market after the treatment.

The hot water also kills microorganisms on the surface of the cantaloupe that contribute to fruit spoilage.

“When you cut the melon, you are moving those microorganisms from the surface to the flesh,” he said. “It takes a little longer for (treated cantaloupe) to spoil compared to non-treated fruit,” he said.

Researchers are also looking at chlorine dioxide in experiments on fresh produce safety. The chemical is not yet approved for use on fresh produce by federal regulatory agencies, but researchers have been looking at its potential application to cantaloupes, leafy greens and tomatoes.