August 1, 2007 Food scientists at The Ohio State University wanted to see if cooler water could kill bacteria on dirty dishes like E. coli and salmonella. The study found that even when dishes were washed in cooler temperatures, it still cleaned enough bacteria away to levels accepted in the food and drug administration's food code.
You've seen the restaurant reports -- health departments shut down hundreds of restaurants each week because they don't meet health standards. E. coli and salmonella outbreaks make customers sick -- dirty dishes could be to blame.
Restaurants clean plate after plate after plate -- but just how clean are the plates you're eating off?
"You just can't go on looks -- you really have to have good techniques," said Melvin Pascall, food scientist at The Ohio State University.
The FDA recommends restaurants follow a three-step process when washing dishes -- scrub in soapy hot water at an uncomfortable 110 degrees Fahrenheit, rinse with clean water, and then soak in sanitizer.
Food scientists at The Ohio State University wanted to see if cooler water could still kill bacteria.
"Micro-organisms are smaller than our naked eyes can detect," Pascall said.
Milk and cheese provide a place for bacteria to grow, lipstick keeps bacteria from sticking.
"The thing is -- you want to clean the utensil and make sure it's free from bacteria -- period," said Pascall. Dishes are not created equally -- compared to ceramic plates, steel knives, spoons, forks and plastic trays are prime growing spots for bacteria.
The study also found that even when dishes were washed in cooler temperatures, it still cleaned enough bacteria away to levels accepted in the food and drug administration's food code.
Although the study was aimed at restaurants, food scientists say to stay safe at home, wash your dishes right after using them, before the food dries and bacteria grows.
BACKGROUND: New research at Ohio State University reveals some interesting insights into how clean dishes become using manual washing. Scientists found that even when they washed dishes in cooler-than-recommended water, the bacteria levels on the dishware dropped to levels acceptable under current FDA regulations. This means that restaurant employees can use a more comfortable dishwashing technique and still end up with clean dishes.
LATHER, RINSE, REPEAT: 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. Employees often use water that is cooler than 110 degrees F -- the minimum washing temperature recommended by the FDA -- because it is uncomfortably hot. The FDA also requires that washing cause a 100,000-fold drop in the amounts of bacteria on those dishes.
ABOUT THE EXPERIMENT: To investigate the effectiveness of lower-temperature dishwashing tactics, the OSU researchers coated dishes individually with cheese, eggs, jelly, lipstick and milk, and then added Escherichia coli and Listeria innocua bacteria. Both these contaminants can survive for long periods of time if they make their way onto food dried onto dishes. If those dishes are not thoroughly washed, they can sometimes cause food-borne disease outbreaks. They let the food dry on the dishes for an hour, and then used different combinations of washing, rinsing and sanitizing before measuring the levels of microscopic organisms still clinging to the dishes, thereby determining the effectiveness of the cleaning.
WHAT THEY FOUND: The OSU researchers found that washing dishes in hot dishwater, 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. However, all dishes are not created equal. Compared to ceramic plates, steel knives, spoons and plastic trays, steel forks proved more stubborn about hanging onto bacterial contamination, largely because of the prongs. They recommended taking extra time to wash forks, especially those covered in sticky substances like cheese. Also, milk dried onto glasses protected bacteria more than any other food, although it is still unclear why that should be the case. Based on their findings, the OSU scientists recommend washing dishes right away before food dries, since otherwise bacteria will grow on them. It saves washing time and gets rid of problematic places where bacteria might be able to survive washing and drying.
The American Society for Microbiology contributed to the information contained in the TV portion of this report.
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.