Moldy strawberries? Not for 9 days with UV LEDs

Strawberries are a treat to treasure, but if stashed in the fridge for a handful of days, they're likely to grow an undesirable goatee of mold. Those days may be numbered, according to researchers who've shown that exposing the red fruit to low levels of ultraviolet light doubles their shelf life.

The proof-of-concept results stem from a challenge given by an undisclosed refrigerator manufacturer to the maker of new light-emitting diodes (LEDs) that emit ultraviolet (UV) light at wavelengths found in sunlight transmitted through the atmosphere.

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What exactly the lights are doing to the berries to stave off mold is unknown, according to Steven Britz, a researcher at the U.S. Department of Agriculture's Food Components and Health Laboratory, who led the experiments as a side project with funding from the LED maker, Sensor Electronic Technology Inc.

"We have a hypothesis that we have tested," he told NBC News. "We could be activating defense genes in the strawberry in part. That's been shown by other people in published papers."

Other possibilities include a germicidal effect on the mold spores or a modification of the cell walls on the strawberries that somehow make them less hospitable to the growth of mold.

Whatever the reason, tests in Britz's lab found that when the strawberries are stored in a fridge under the lights continuously, spoilage was delayed for at least nine days, which is more than 50 percent longer than they unexposed berries.

Analysis of the strawberries revealed slightly higher levels of the red pigment in strawberries, normal levels of sugars and acidity, he noted.

"The strawberries, from what we could deduce, looked good," Britz said.

But did the researchers eat them?

"No, we didn’t' have enough," he said, explaining that the experimental setup allowed for just four strawberries in each container, which they kept for other analytical tests. "But they looked good, and they smelled good … I wouldn't have hesitated to eat them."

Britz will present the results of the tests at the Conference on Lasers and Electro-Optics 2013 being held June 9-14 in San Jose, Calif.

John Roach is a contributing writer for NBC News. To learn more about him, visit his website.