This is the germiest surface in your kitchen, new study finds

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Move over, cutting boards. According to a new study, there’s a new category of items to watch out for when guarding against potential kitchen mishaps.

A November 2022 study in the Journal of Food Protection to determine the prevalence of cross-contamination across a variety of kitchen surfaces during a meal preparation found that spice containers had the highest degree of cross-contamination of any of the surfaces analyzed in the study. This includes surfaces like cutting boards, countertops and even trash cans.

For the study, researchers asked 371 individuals to prepare a meal of a ready-to-eat lettuce salad and turkey patties, the latter which contained the bacteriophage MS2 (which is not harmful to humans as a tracer organism.)

Half of the participants in the study were shown a video on proper thermometer use before preparing their meal. Then, when they were done, researchers took environmental samples to detect cross-contamination of MS2 bacteria on various surfaces that included countertops and other surfaces like refrigerator handles, kitchen utensils, cleaning areas and more.

While most of the meal preparation events resulted in two or fewer environmental cross-contamination, 81% of the time, one or more surfaces resulted in cross-contamination, meaning that most of the time people unknowingly spread germs around the kitchen. The study also mentions one event where there were 10 events of cross-contamination in a single burger-making session, meaning that one of the study’s participants really needs to enroll in cooking safety 101.

“It’s really hard to go into someone’s home to conduct research but when you bring them to a simulated home setting, we get better information about where someone might make mistakes,” Benjamin Chapman, Ph.D., professor and food safety specialist in the department of Agricultural and Human Sciences at North Carolina State University tells TODAY.com.

As a senior author on the study, Chapman says he handled design analysis and oversaw the students that did the work swabbing surfaces of the participants, who were recruited from Johnson and Wake counties in North Carolina.

Chapman says that researchers were surprised at the results. By far the highest culprit for cross-contamination in the study was spice containers at 48% of the time. Common cross-contamination problem areas like trash can lids, cutting boards, frying pan handles and faucets all accounted for less than 20% positivity rates in the study.

“It was a little bit of a surprise to us that we saw so much contamination on spice bottles since we were really invested in other parts of the kitchen,” Chapman says, adding that spots like refrigerator handles, the trash and faucets were expected to be the highest instance of cross-contamination. “But spice containers really popped out as the number one place that we saw contaminated.”

According to the USDA’s Food Safety and Inspection Service, cross-contamination happens when harmful bacteria on food like raw meat, poultry, eggs, and seafood transfers to other foods, cutting boards and utensils. It happens when these items are not handled properly, like when you don’t wash your hands at the right times when preparing a meal. Research shows that this was the case in this particular study.

“When we looked at the data and reviewed the video of what people were doing, there wasn’t a lot of hand washing after handling the raw turkey before spicing the turkey mixture up with spice containers,” Chapman said. “So it really came down to hand washing.”

Another 2021 observational study by the FSIS in which participants were recorded cooking in a test kitchen found that 97% of participants failed to successfully wash their hands at the times they should have. That astounding figure is what drives Chapman and other experts to continue their research into how we all can safely prepare our burgers, salmon tacos and more at mealtimes.

Chapman asserts that the results of this study don't mean you should throw away your spice containers. He says if you’re really concerned about your spice containers you can certainly clean and sanitize them. “To me, it’s not a cause for concern,” he says.

According to the Centers for Disease Control, four specific groups are most at risk for foodborne illness that is caused by eating or drinking something contaminated with disease-causing germs. Those groups are: elderly adults aged 65 and older, small children under 5, pregnant women and people with weakened immune systems.

“Essentially, those four groups are more at risk of foodborne illness,” Chapman says. “It’s not to say that others don’t get sick — because they do — but but a higher proportion of individuals in those populations get sick compared to others.”

Chapman says this study is one of a series that he and others have done over the last few years have looked at different types of foods that people may commonly prepare. He adds that the results of these studies help researchers build better educational materials to try to increase knowledge of what harmful practices we may unknowingly be doing when we cook.

“I really suggest that people think a lot about hand washing during meal preparation,” Chapman says. “Think about all the things in your kitchen that you might be touching.”

This article was originally published on TODAY.com