Where You Will Find The Most Germs In Your Kitchen, And It’s Not Where You Think

A study published in the Journal of Food Protection revealed that spice jars are the dirtiest items in kitchens due to the rate at which cross-contamination occurs when preparing food.

By Kari Apted | Published

kitchen germs clean house

There’s one area of your kitchen that harbors the most germs, and it probably doesn’t even rank in your top five guesses. It’s not the sink, the floor, the countertops, or even the cutting board. A study published in the November issue of the Journal of Food Protection measured the amount of cross-contamination that takes place during cooking and discovered that spice jars are the most heavily contaminated items in the kitchen.

The study’s researchers were led by Donald Schaffner, a professor in the Department of Food Science at Rutgers School of Environmental and Biological Science. The team recruited 371 participants to help them measure the “prevalence and degree of cross-contamination across a variety of kitchen surfaces during a consumer meal preparation event.” Participants were asked to prepare a meal including a lettuce salad and turkey patties that had been inoculated with the bacteriophage MS2, a good tracer organism because it’s not harmful to humans.

Participants weren’t informed that their food safety behaviors were being monitored until after the meal prep, but half of the participants were shown a video on proper thermometer use. The kitchen size varied from large teaching kitchens to small, apartment-sized kitchens. Instructions included using various spices to create a seasoning recipe for the turkey burgers.

After the meal prep, researchers took samples from the cooking area to measure MS2 cross-contamination. The researchers found that, for most surfaces, cross-contamination did not exceed 20%, a figure in line with previous studies of kitchen cross-contamination. However, 48% of the spice jars showed evidence of germ contamination.

“We were surprised because we had not seen evidence of spice container contamination before,” Schaffner told Food Safety News. “Most research on the cross-contamination of kitchen surfaces due to handling of raw meat or poultry products has focused on kitchen cutting boards or faucet handles and has neglected surfaces like spice containers, trash bin lids, and other kitchen utensils. This makes this study and similar studies from members of this group more comprehensive than previous studies.”

No other swabbed surfaces came close to the spice jars’ 48% level of cross-contamination. Cutting boards were the second most contaminated surfaces, while trash can lids ranked third. Surprisingly, sink faucet handles were the least contaminated of the surfaces studied.

The study was commissioned by the U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS) to better understand where and how kitchen cross-contamination takes place. Although many of us likely already know how to practice good cooking hygiene, the study indicates that we need to be more careful with washing our hands during the cooking process. Properly cleaning everything we touch afterward—including spice jars—can cut down on the spread of potentially harmful germs.

You don’t need to douse your spice jars in bleach to rid them of germs, however. A simple wipe-down with a cloth dipped into equal parts white vinegar and water is sufficient. Vinegar is a natural disinfectant, ideal for kitchen use because you don’t have to worry about strong cleaning chemicals getting into your favorite spices.

According to Maids by Trade, a cleaning service, it’s wise to empty and thoroughly clean your spice jars periodically. Empty the spices into small bowls or containers and hand wash the jars and lids in hot, soapy water. Rinse them in hot water and allow them to fully air dry on a kitchen counter rack before pouring the spices back into the jars.

It’s also good to label your spices with the date you bought them so you know when they are ready to toss. While cooking with old spices won’t make you sick, they won’t impart the full flavor of fresh spices. Most whole or ground spices and herbs have a shelf life of one to two years, while ground roots (like ginger) and mustard seeds last for two to three years.