Aug. 17, 2001 -- The next time you put your clean dishes away, you may want to be extra careful they're dry.
Why? Because dishes stored away while wet can become contaminated with bacteria, according to a study in the August issue of the Journal of the American Dietetic Association.
"Any time you hold wet dishes you have the chance they'll get recontaminated, because a moist, warm environment provides good conditions for bacterial growth," says Nancy Reed, RD, LD. "There are bacteria everywhere. If at all possible, do dry your dishes before you store them." Reed, who was not involved in the study, is clinical nutrition director for Mercy Medical Center in Baltimore, Md.
In the study, researchers identified bacteria on 100 dishes used to serve food at the Veterans Affairs Medical Center in Portland, Ore., and then all of them were washed in a commercial dishwasher. Half of them were air-dried for 24 hours, while half were stacked while wet. "No significant difference was found between air-dried and and wet-nested plates in the first 24 hours, but a significant difference was found after 48 hours," the authors write.
A food code developed by the FDA specifies that all dishes should be air-dried before being stacked and stored. However, most of us can recall walking into a cafeteria and pulling a wet plate from a stack of dishes.
"That's happened to me so many times," says Nelda Mercer RD. "In a huge establishment, plates don't stay in the stack very long, because turnover is so great. This study found bacterial contamination when plates were stacked wet for more than 24 hours, and that suggests there might be a real problem in places like a church kitchen or community center if plates are stacked wet and then left to sit for a substantial time. Anytime you use volunteers to cook or serve food, make sure they are trained in safe food-handling practices." Mercer is a nutrition specialist consultant for the Michigan Department of Community Health and a spokesperson for the American Dietetic Association.
"Drying dishes keeps bacteria from multiplying, and most food-borne infections are related to relatively large numbers of organisms," says David Sewell, PhD, co-author of the study. "I am not aware of any well-documented cases where someone has actually contracted a food-borne illness from a contaminated plate. This is a relatively small pilot study, designed to point out that storing dishes while wet does create an environment in which bacteria are more likely to grow." Sewell is director of the microbiology section of the pathology and lab medicine service at the Veterans Affairs Medical Center, and professor of pathology at Oregon Health Sciences University, both in Portland.
People may be at higher risk at home than in a large institution, because commercial dishwashers use hotter water than home dishwashers, suggests Reed. "At home, it's always better to air dry your dishes than to use a dish towel, because a dish towel can harbor all sorts of bacteria. You wipe your hands with it, you use it to dry the counter, and then you use it to dry the dishes!"
Mercer agrees. "Air-drying is best. Or, if you do want to hand-dry your dishes at home, use a clean cloth, fresh from the drawer."