COLUMBUS , Ohio New research at Ohio State University answers an infectious question about eating at restaurants: How clean are manually washed dishes?
Jaesung Lee and Melvin Pascall found that even when they washed dishes in cooler-than-recommended water, numbers of bacteria on the dishware dropped to levels accepted in the Food and Drug Administration's Food Code. They also found that certain foodsespecially cheese and milkcan be safe havens for bacteria when dried onto dishware. Lipstick, however, proved to be dangerous to bacteria.
"After washing, there were lipstick stains still left on a few glasses, but it was the least hospitable substance for bacteria," Pascall said. "It seems to have antimicrobial properties, which was a big surprise to us."
Lee, a doctoral candidate of food, agricultural and biological engineering, and Pascall, assistant professor of food science and technology, published their findings in the Journal of Food Engineering.
When restaurants manually wash dishes, they follow a three-step process: Dishes are washed and scrubbed in soapy water, rinsed with clean water, and finally soaked in water containing germ-killing sanitizers. But employees often use water that is cooler than 110 degrees Fahrenheitthe minimum washing temperature recommended by the FDAbecause it is uncomfortably hot. The FDA also requires that washing cause a 100,000-fold drop in amounts of bacteria on those dishes.
To investigate effective lower-temperature dishwashing tactics, the researchers coated dishes individually with cheese, eggs, jelly, lipstick, and milk, and then added Escherichia coli and Listeria innocua bacteria. Contaminants like E. coli and L. innocua can survive for long periods of time if they make their way into food dried onto dishes. If those dishes aren't thoroughly washed, they can sometimes cause food-borne disease outbreaks.