Ravishankar's research has shown that simple measures can go a long way in lowering the risks. Her team recently submitted a publication showing that washing alone reduces bacteria on produce by up to 100 fold.

The researchers looked at organic romaine lettuce, iceberg lettuce, baby spinach and bunched spinach; they compared plain washing, hydrogen peroxide washing, and treating the greens with plant extracts.

"Using plant extracts, we were able to reduce the bacterial load by over 1,000-fold," Ravishankar said. "They were even better than hydrogen peroxide. The good thing about plant extracts is that you have that activity over time, they keep acting. Hydrogen peroxide works only momentarily."

Applied in commercial settings, these measures could make a big difference, especially for organic growers, who are unable to treat their produce with high concentrations of certain chemicals like bleach.

According to Ravishankar, 1,000-fold reduction in bacterial contamination is a major step forward.

"In the real world, you won't find 1 million disease-causing bacteria on a lettuce head. The pathogens are going to be present in smaller quantities compared with the background flora," she explained. "A healthy individual should be able to tolerate some pathogenic cells. You would need to ingest at least between 100 and 1,000 cells to get sick. But small children or elderly people with compromised immune systems are at a higher risk. In children, as few as 10 cells can cause sickness."

In collaboration with Gerba, Ravishankar's team is looking at what doses pathogens become a risk. Gerba's team will develop a mathematical model based on the results obtained in the experiments of the Ravishankar lab.

"Let's say you had so many cells on lettuce under certain conditions, what is the risk to consumers? Those are the kinds of questions we want to answer," she said.

In another line of research, Ravishankar's group is investigating how edible films made from plant parts can be used as wrappers or ingredients of bagged produce and meats.

The preliminary results are promising: Wrapping raw chicken meat in an edible apple film containing carvacrol, the active ingredient of oregano oil, effectively inactivated foodborne bacteria over a three-day storage, and the same substance reduced E. coli on spinach by about 1,000 fold.

"The longer the exposure, the more bacteria are killed," Ravishankar said. "Because of the time-dependent action of these substance, they are ideal candidates for increasing food safety while the products are in transit to the consumer and during storage."