N.C. Research Campus scientists aim for safer organic produce

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Posted: Monday, March 11, 2013 12:23 pm

KANNAPOLIS, N.C. – A group of scientists at the University of Tennessee Institute of Agriculture and North Carolina State University are working together to improve the safety of organic produce – naturally.

Their study, “Alternative Post-harvest Washing Solutions to Enhance the Microbial Safety and Quality of Organic Fresh Produce,” began last fall.

The four-year, multidisciplinary project is supported by a nearly $2 million grant from the U.S. Department of Agriculture’s Organic Agriculture Research and Extension Initiative (OREI) program. Qixin Zhong, an associate professor in the UT Department of Food Science and Technology, leads the initiative.

Penelope Perkins-Veazie, a post-harvest physiologist at N.C. State’s Plants for Human Health Institute (PHHI) on the North Carolina Research Campus, said the study will focus on tomatoes, cantaloupes and romaine lettuce — some of the dirtiest fruits and vegetables on the market in terms of food-borne illness.

“These things tend to be the ones we get repeated outbreaks on,” she said.

The group hopes to provide effective sanitization in the form of alternative organic anti-microbials — naturally occurring substances such as organic essential oils that fight pathogens like E. coli — added to post-harvest wash water.

E. coli, salmonella and listeria contaminate produce, and Perkins-Veazie said sources can be animal manure used for fertilizer, wildlife droppings or any number of unknown sources. She added that listeria comes from the soil, so contamination is often unavoidable.

Many conventional and organic harvesters use a treatment of chlorine dioxide gas or peroxyacetic acid to disinfect produce.

She said many organic growers are opposed to the use of chlorine because of issues with water discharge, level monitoring and the narrow range of amounts needed for safety and effectiveness.

“They do it, but they’d rather have another choice,” she said. The above-mentioned chemical treatments also only disinfect the surface of the produce, and pathogens underneath can survive.

“If you have something that’s under the peel, you’re not going to remove it,” she said. “And unfortunately with microbes we’re always worried about that.”

Researchers will use plant-derived compounds like cinnamon and clove essential oils — which have a history of preservative use since the ancient Egyptians — and test how plants react to them and whether they provide anti-microbial protection.

They’ll start in the lab, then move to the field, testing the compounds’ effectiveness and how well they can be applied in a real setting.

As part of the project, the researchers also will evaluate the economic feasibility of their work and impact on the shelf life of various types of organic produce, according to information provided by the Plants for Human Health Institute.

To achieve that goal, researchers are partnering with a group of organic produce growers who will provide feedback throughout the study. In addition, the team will share research findings through webcasts, written fact sheets and a series of workshops held in Tennessee and North Carolina.

Perkins-Veazie said the study has revolutionary potential.

“You could invent an entirely new sanitizer,” she said, one that has been impossible or impractical to formulate in the past.

She added there is a sensory component to the USDA grant that will allow researchers to test how strongly-flavored essential oils alter the taste of produce upon application.

“What will happen if you spray cinnamon-scented oil on romaine lettuce?” she asked. “Will it be objectionable, will we even notice, or will it actually enhance the flavor of the lettuce?”

And plants may react to the oils by creating complicated defensive mechanisms, some of which create compounds like anti-inflammatory agent quercitin that are important to human health.

“We can show an extra impact of this oil,” she said. “So not only is it going to be killing human pathogens, but it might be elevating a compound of interest.”

North Carolina State University’s project team includes an interdisciplinary group of faculty from the Plants for Human Health Institute, N.C. Cooperative Extension and the Department of Food, Bioprocessing and Nutrition Sciences, all of which are part of the university’s College of Agriculture and Life Sciences (CALS).

Other NCSU researchers on the study are Dr. Jeanine Davis, NCSU associate professor and extension specialist in organic crops; Dr. MaryAnne Drake, NCSU professor in sensory analysis and flavor chemistry; Diane Ducharme, GAPs program coordinator and extension associate in horticulture and food safety with PHHI.