Scientists from the U.S. Department of Agriculture’s Agricultural Research Service joined researchers from Rutgers University’s Department of Food Science for the study. The ARS staffers involved were Tony Jin, Xuetong Fan and Linshu Liu. Researchers from Rutgers were Soumi Ray and Kit L. Yam.
They produced and tested polylactic acid (PLA) packaging film with sodium chlorite and citric acid powder. The film was designed to react with water released by fresh produce to create chlorine dioxide gas inside the packaging.
Scientists from the USDA and Rutgers University produced a special packaging film that releases chlorine dioxide gas into fresh produce containers to kill foodborne pathogens.Using grape tomatoes in plastic clamshells, the scientists taped pieces of the special film to the inside of the lids. The tomatoes had first been cleaned to remove background pathogens and were then doused with three kinds of salmonella and E. coli O157-H7.
The researchers documented the amount of salmonella and E. coli was 1,000 times smaller — reaching undetectable levels — on tomatoes in clamshells with the PLA film compared to tomatoes in clamshells without the film. The tests were conducted with the tomatoes stored at temperatures consistent with transportation and storage temperatures used in the supply chain.
Such packing is feasible and definitely needed for fresh produce, the researchers wrote.
Citing an increasing number of documented foodborne illness outbreaks associated with fresh produce in recent years, the researchers said in their report that “there is an urgent need for intervention methods used as nonthermal in-package pasteurization for (ready-to-eat) foods.”
“The possibility of human pathogen contamination on foods after sanitization or thermal processing could result from package machines, package materials, poor hygiene by packinghouse workers or supermarket employees, or cross contamination in the supermarket during unpacking, display, in-store fresh-cut processing, or handling,” the researchers wrote.
In addition to testing for pathogens on the tomatoes from the clamshells with the special PLA film, the researchers tested color, texture and flavor of the tomatoes after two, seven, 14 and 21 days. They reported no significant changes in color, texture and taste.
They also noted that the tomato skins did not suffer wrinkling that had been reported in previous studies using chlorine dioxide gas with other exposure methods.
Chlorine dioxide is a “well-established antimicrobial agent,” the researchers wrote, and has been used in gas and liquid forms. However, the gas-producing film would provide better pathogen reduction.
“The (chlorine dioxide-releasing) packaging provides advantages over the current ClO2 washing practice by avoiding possible cross-contamination or recontamination of foods after packaging and before consumption,” the scientists wrote.
The antimicrobial packaging could be used for other fresh produce that generate moisture inside a package.
“By adjusting PLA percentage … (a) different quantity of ClO2 released from the film could be achieved for different kinds of fresh produce. The application could also be extended to non-moisture-generated foods, when a drop of water is injected into the package to activate ClO2 release.”