Scientists have estimated that 99 percent of food-borne illnesses from leafy greens can be traced back to disinfection issues. As a result, the team has developed a different approach to attacking the bacteria, most notably E. coli, which is the cause of many outbreaks. Using a parallel-plate flow chamber system that Walker developed, the researchers tested the real-time attachment and detachment of bacteria to the outer layer of spinach leaves.(How to Keep Greens Fresh | Kitchen Tips)
At low-bleach concentrations, the bacteria fell off the leaves but remained alive. At the higher concentrations used commercially, however, all of the bacteria were killed. "We found that because of the topology of the spinach leaf, nearly 15 percent of the surface may 'see' a bleach concentration that is 1,000-times less than that of the rinse solution," Kinsinger noted.
In some cases, that translated to a 90 percent bacterial survival in their tests -- and a high risk for cross contamination. To reduce that risk, the researchers are optimising an inexpensive titanium dioxide (TiO2) photocatalyst that companies could add to the rinse water or use to coat equipment surfaces that come in contact with the leaves as they are processed. When TiO2 absorbs light, it produces a strong oxidant that kills bacteria completely.
The team presented their work at the national meeting and exposition of the American Chemical Society (ACS) in Boston this week.