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How Can You Be Sure Those Dishes are Clean?

The highest bacteria counts can sometimes be found where you least expect them. Kitchen counters are breeding places for germs?but what about restaurants?

Most restaurants use automatic dishwashers, but small restaurants and bars often wash dishes and glassware by hand. New research answers a basic question about eating and drinking at these places: How clean are manually washed dishes?

Researchers 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 foods?especially cheese and milk?can be safe havens for bacteria when dried onto dishware. Lipstick, however, proved to be dangerous to bacteria (which is good news people who worry about exchanging germs while kissing!)

Pascall says, "After washing, there were lipstick stains still left on a few glasses, but it was the least hospitable substance for bacteria. It seems to have antimicrobial properties, which was a big surprise to us."

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 Fahrenheit?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 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.

After letting the food dry on to the dishes for an hour?a plausible wait in a busy restaurant dish room?they gave each utensil a few scrubs per side and measured the amount of microscopic organisms still clinging to the dishes. 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.

Pascall says, "We wanted to show that employees could use a more comfortable washing technique and still get clean dishes. 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 says. "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 says that while scientists know that milk is a good growth medium in the laboratory, why it adheres to glass so well isn't clearly understood. He says, "Milk is an area of research we'd like to explore further."

How can this research help those of us who wash dishes by hand at home? Pascall says, "Leaving food on eating utensils and dishes could easily cause bacteria to grow on them, especially if it's moist. The best thing you can do is wash your dishes off right away, before the food dries. It saves washing time and gets rid of places where bacteria can survive drying and washing."

And don't forget to microwave your sponge for 2 minutes every other day!

One way to eat is to order room service. When Whitley was in a hotel in Toronto on a book tour, he heard a knock on the door. He thought it was the room service waiter, coming to pick up his dirty dishes, but it turned out to be the most extraordinary man he's ever met.

Art credit: freeimages.co.uk

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