Onion X-rays

The Vidalia onion is Georgia’s official state vegetable and No. 1 fresh vegetable crop. But like any major crop, it has its fair share of problems-ones UGA researchers want to fix.

Onions are the third most valuable vegetable in the U.S. Worldwide, they’re the second most valuable vegetable.

Before onions get to consumers, growers and packers must deal with disease, storage and handling problems. College of Agricultural and Environmental Sciences researchers are leading a national team to solve some of these problems with help from a three-year $774,581 grant from the U.S. Department of Agriculture National Institute of Food and Agriculture Specialty Crop Research Initiative.

The team’s goals are to detect infections and rot that hide deep within onions right after harvest and then while in storage. They also want to find a better way to get rid of rotten onions, according to UGA biological and agricultural engineer Changying “Charlie” Li, who oversees the project.

The research team includes UGA plant pathologist Ronald Gitaitis and CAES engineers Gary Hawkins, Bill Tollner and Chi Thai, food scientist Rob Shewfelt and horticulturist Dan MacLean. Other universities or cooperators on the team are Colorado State, Mississippi State, Auburn, Idaho, Cornell, Arizona, Tsinghua (in China) and Georgia Southern.

“Can we reduce the amount of damage in onions out there in the retail market?” said Gitaitis. “Improving the detection, that’s what this research is about.”

After onions are harvested, workers check them for blemishes, diseases and other issues. Onions that make the grade are sent to grocery stores or are cured and stored. Onions that don’t make the grade are tossed aside.

Human eyes and hands can’t detect all onion problems. The team wants to develop an onion sorting machine using X-ray and hyperspectral imaging, which could detect many of the problems. Hyperspectral imaging can detect infrared, ultraviolet and visible light and predict sugar, water and hydrogen components of onions. X-ray machines can look through the onion’s layers and see the diseases.

“Onions are actually subjected to 60 post-harvest diseases,” Li said.

Onions are stored in big warehouse rooms for four to six months. If one onion is infected, the problem can easily spread.

The team is working to develop technology that will “smell” when an onion goes bad. They’re testing an electronic nose to see if it can detect disease and sensors to see if they can trace the location of those diseases.

“It’s a device similar to those they use to detect possible terrorist attacks,” Li said. “It measures the air and can detect the location of the problem.”

Culled or bad onions are often dumped in fields. Diseased onions put back on fields can lead to more diseases.

Hawkins, a CAES pollution prevention and alternative energy specialist, is working to turn unwanted onions into fuel, specifically methane gas. To do so, he shuts them in containers called anaerobic digesters, which are void of oxygen and contain bacteria. The digesting onions produce methane gas that can be used to heat buildings or to run electricity-producing generators.

Automated systems can help farmers and packers save money. Fewer rotting onions can generate more income in the 13 rural Georgia counties where they are grown. But a new sorting system could cost jobs. Part of the grant will be used to analyze the possible effects of automated onion sorting.