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UGA Scientist Uses X-rays to Sort Fruits, Vegetables

You search for the best apples, handle them with kid gloves and still throw out half when the hidden bruises show up a few days later. You'd need X-ray vision to pick only the perfect apples.

That's exactly what University of Georgia researchers concluded. So they developed a new grading system to make sure the bad apples never reach supermarket shelves.

How Scientists See Inside Fruit

Using medical X-ray machines, Bill Tollner can detect imperfections in fruits and vegetables before anyone can see them.

S. Omahen, UGA CAES
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LOOKING INSIDE FRUIT with X-rays helps prevent damaged fruit from reaching markets. Using a medical x-ray machine, Bill Tollner, above, can grade produce and help farmers and distributors learn which fruits are already damaged and will deteriorate in storage.

"With apples, bruises are a big problem," Tollner said. "We can detect old bruises before they can be seen by the human eye."

An engineer with the UGA College of Agricultural and Environmental Sciences, Tollner was using X-rays to study soil layers when a colleague suggested he try it with food products.

Why use X-rays?

"One of our food scientists had been working on water core problems in apples," he said. "He asked me to use the X-ray equipment on them."

Water core is a condition that causes apples' internal moisture to increase.

S. Omahen, UGA CAES
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CHECKING THE DATA on fruit in an X-ray machine allows Bill Tollner, above, to look inside the fruit without cutting into it. This equipment is the same as used for medical x- rays.

"It occurs in Red Delicious apples. If you eat the apple right away, it has a delicious taste," he said. "You just can't store them, which creates a big problem for apple processors."

Water-core apples develop dots near the veins. Over time, the dots turn brown.

Tollner found the X-ray equipment can easily detect water core in apples. It can "see" many other defects in carrots, onions and celery, too.

"For example, some onion diseases cause air gaps between the rings," he said. "The X-rays clearly show these gaps well before the onion shows visible signs of disease."

This method helps the fruit industry.

This new grading method could be especially useful for apple and onion processors who commonly store their products.

"The whole goal is to keep the product on the shelf longer," Tollner said. "Using this equipment, processors can pull out bad fruit before storing it side by side with good fruit."

The new X-ray grading system has received good reviews from apple processors in New York and West Virginia. "I plan to present the new process to Georgia's Vidalia onion growers this month at an upcoming conference," he said.

Tollner is also working with U.S. Department of Agriculture researchers at the USDA Fruit Research Station in West Virginia.

The fruit industry wants the systems

"They've developed an optical grader. We'd like to combine the two machines," he said. "Eventually, we'd like to see apples and other food items come through the sorter where the X-rays will find the internal defects and the optical viewer the surface defects."

Mechanical grading systems like these could help food processors deal with labor shortages.

"We're coming to a point in our country where labor to inspect food products just isn't there," Tollner said. "People feel they have more stimulating things to do than inspect food for minimum wage."

Research proves its safety

When radiation and food products come in contact, many shoppers voice safety concerns at first. Tollner said the radiation levels used in this process are lower than the levels used in dental X-rays.

"The canning industry uses X-rays to detect metal fragments to insure safety," he said. "With this process, I'm using them to improve the quality and safety of food before consumers buy it."

(Sharon Omahen is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)

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