Lee and Pascall discovered that washing dishes in hot dish water, followed by soaking in extra sanitizers, eliminated almost all of the bacteria on them, even when coated with dried-on cheese. But dishes washed in soapy room-temperature water, rinsed, and then weakly sanitized with ammonium-based chemicals also achieved FDA-acceptable results.
The find is important because acceptable sanitization can be achieved with cooler dish-washing water, as dishes washed in room-temperature water and then rinsed in more-concentrated sanitizers achieved results comparable to higher-temperature alternatives.
"We wanted to show that employees could use a more comfortable washing technique and still get clean dishes," Pascall said. "We were able to do that, and we did it by using different combinations of washing, rinsing, and sanitizing."
But all dishes are not created equal. Compared to ceramic plates, steel knives, spoons, and plastic trays, steel forks seemed to be the best home for bacterial contaminants.
"The prongs of forks actually shield food from the action of scrubbing," Pascall said. "Taking extra time to wash forks is a good idea, especially those covered with sticky foods like cheese."
Although cheesy forks were the most problematic utensil, milk dried onto glasses protected bacteria more than any other food. Pascall explained that milk is a good growth medium in the laboratory, but why it adheres to glass so well isn't clearly understood.
"Milk is an area of research we'd like to explore further," Pascall said. "We want to find ways to safely and quickly remove milk dried on glasses."
The research aimed to explore restaurant dishwashing conditions, but Pascall explained that homeowners can benefit from the findings, too.