Purdue University researchers have developed detection technology that allows a typical smartphone to analyze produce for foodborne pathogens such as E. coli O157:H7, which has been linked to a deadly outbreak in romaine lettuce.

The technology involves both hardware—a smartphone cradle—and software in the form of an application that is downloaded on the phone. The combination allows the smartphone to be used as an on-site luminometer, an instrument used to measure light.

The lettuce or other produce is rinsed with an enrichment liquid containing a modified phage, a virus for bacteria. The phage then infects harmful foodborne bacteria so that when a substrate is added, they emit light, which is detected by the smartphone’s camera through the downloaded app and a green dot appears on the screen.

The cradle on the phone maximizes the photon collection by using diffusive reflection material to help capture a maximum amount of light, which may not be visible by the naked eye.

“This technology could be used on a farm or in a food processing factory to provide on-the-spot detection,” said Euiwon Bae, a senior research scientist in the Purdue School of Mechanical Engineering, who developed the technology along with Bruce Applegate, a professor in the Purdue Department of Food Science. “This rapid detection is critical for getting safe produce to consumers.”

The smartphone technology, coupled with the phage, helps reduce the typical amount of time it takes to test food samples for possible foodborne illnesses. The current process involves gathering a physical sample and then shipping it to a lab and waiting several days for the results.