It is estimated that 48 million cases of foodborne illness occur in the United States each year, and up to 20% of these may be related to food prepared at home.1 This means that the food you cook in your own kitchen has the potential to make you sick and potentially transfer these disease-causing bacteria to other nearby surfaces.
While you’re probably aware of the risks of a dirty sponge being used too often – or that even your kitchen sink could become a reservoir for bacteria – when was the last time you cleaned your spice jar?
It turns out that these humble kitchen staples can be one of the biggest culprits in cross-contamination and may be the highest contamination risk in the kitchen.
48% of spice containers are contaminated
In a study commissioned by the U.S. Department of Agriculture’s Food Safety and Inspection Service,2 Researchers at Rutgers University’s School of Environmental and Biological Sciences and colleagues analyzed how 371 adults cooked turkey burgers in kitchens ranging from apartment-style kitchens to those in teaching settings and food banks.3
Poultry, including chicken and turkey, is one of the leading sources of Campylobacter-related illnesses, a bacteria responsible for 800,000 foodborne infections in the United States each year4 As noted in the Journal of Food Protection:5
“According to the Interagency Food Safety Analysis Collaborative, 40.5% of non-typhoid salmonella illnesses are attributed to products regulated by the Food Safety and Inspection Service (FSIS), and 78.8% of all non-dairy Campylobacter illnesses are attributed to FSIS-regulated products. Products, which include: chicken, turkey, other meat or poultry, beef, pork, and game (0.6%), in descending order.
Clearly, improper handling of raw poultry, such as improper cooking, improper handwashing, and cross-contamination of ready-to-eat (RTE) foods in the home, may allow such pathogens to cause foodborne illness. “
To determine how common cross-contamination of kitchen surfaces is during common meal preparation, researchers asked participants to prepare a meal of raw turkey pot pie, dressing, and prepackaged salad. The meat was inoculated with a bacteriophage called MS2, which served as a tracer throughout the kitchen.
The subjects were unaware that their food safety behaviors were being scrutinized until after the meals were prepared. The researchers then swabbed a variety of common surfaces, including sink faucet handles, kitchen utensils and spice containers. Surprisingly, sink faucet handles were the least contaminated, while spice containers were the most contaminated.
About 48% of spice containers were contaminated with MS2 – significantly higher than most other kitchen surfaces tested, which typically had contamination frequencies below 20%.6 Cutting boards and trash can lids were the second and third most polluted objects. Study co-author Donald Schaffner, Distinguished Professor of Food Science at Rutgers University, said in a press release:7
“Aside from the more obvious surfaces like cutting boards, trash can lids, and refrigerator handles, there are a few other things you need to pay attention to when you want to keep your kitchen clean and hygienic. Our research shows that any spice containers you put in when preparing raw meat can be touched Cross-contamination is possible. You need to be aware of this during or after meal preparation.
… We were surprised because we had not seen evidence of contamination of spice containers before. Most research on cross-contamination of kitchen surfaces from handling raw meat or poultry products has focused on kitchen cutting boards or faucet handles, ignoring surfaces such as spice containers, trash can lids and other kitchen utensils.
That makes this study, and similar studies by members of the team, more comprehensive than previous studies. “
Which other kitchen surfaces have the most bacteria?
Bacteria are almost everywhere, but they’re not always a cause for alarm. However, be careful not to reuse sponges multiple times when washing dishes, as studies have repeatedly listed sponges as one of the most contaminated kitchen items.
In a study of 10 U.S. kitchens, 67% of sponges tested positive for fecal coliforms, while 33% contained E. coli.8 Other studies found that 15.4% of sponge samples contained salmonella, while a hygiene study showed that kitchen sponges had the second highest levels of coliform bacteria, with only drain traps having higher levels.9 As noted in BMC Public Health:10
“During the cleaning process, food particles may adhere to the sponge surface, and moist areas (such as sink areas) may serve as further reservoirs for microorganisms, contaminating the sponge during use. Subsequent handling, storage or disinfection of kitchen sponges Improper use will result in further growth of microorganisms. At room temperature.
Therefore, kitchen sponges are a major source of cross-contamination because they can transmit foodborne pathogens, infectious agents, and spoilage-causing microorganisms to food contact surfaces. “
In another study, researchers analyzed 14 used sponges and found 45 billion microorganisms per square centimeter.11,12 Dish sponges contain the highest numbers of E. coli and other fecal bacteria in the average household, probably because they don’t get replaced as much as they should. Multiple studies have confirmed that kitchen sponges have the highest bacterial count of any household product.13
Can kitchen sponges be washed?
Both sponges and brushes used for dishwashing are susceptible to contamination by non-pathogenic bacteria, although brushes had lower levels in one study.14 Additionally, when a brush is contaminated with salmonella and allowed to dry overnight, the bacteria die faster than a sponge.
“The results of this study suggest that cleaning utensils that dry between uses have lower bacterial counts, including pathogens,” explained the researchers, who recommend using brushes instead of sponges because brushes dry more easily between uses. They also say you can help prevent salmonella from growing in your sponges by:15
- Replace sponge after wear
- Don’t store sponges in the sink
According to the USDA, microwaving a sponge properly can also kill up to 99.99999% of germs, while washing it in the dishwasher can kill 99.9998% of germs.16 If you do put the sponge in the microwave, make sure it doesn’t contain any metallic materials.
MSU also recommends that the sponge should be completely wet when doing this, otherwise it could catch fire or explode during the process.number 17 The wet sponge should be left on high for one minute and then allowed to cool for up to 15 minutes to avoid burns.
Which other kitchen surfaces have the most bacteria?
Cutting boards are another major culprit for harboring dangerous bacteria. Experts recommend having at least two cutting boards, one for foods that are safe to eat raw, such as fruits and vegetables, and another specifically for cutting raw meat, poultry, and fish.
Surfaces used for chopping food can contain bacteria, including E. coli and salmonella. Plastic cutting boards are generally considered safer because they are easier to disinfect. It wasn’t until the 1980s that a UC Davis researcher conducted an investigation and found that although they were easier to sterilize, cutting often left scratches in the plastic, providing a place for bacteria to hide.18
Wood may be harder to disinfect, but it won’t be scratched as easily. Additionally, when comparing wood, plastic, and stainless steel surfaces, Campylobacter survived longest on plastic.19
The USDA recommends washing cutting boards in hot, soapy water after each use and allowing them to air dry completely before putting them away. Bamboo cutting boards are harder than wood, have fewer pores, absorb very little moisture, and are less likely to be scarred by knives. It is important to replace worn plates when they develop grooves that are difficult to clean.20
Your kitchen sink can also be a source of contamination. In one study, participants prepared breakfast with a fruit salad made of raw sausage, eggs, and cantaloupe. When it comes to prep, the kitchen sink is the most commonly contaminated surface, with 34% of people being contaminated. Perhaps as a result, 26 percent of the chopped cantaloupe tested was also contaminated because it may have been washed in a dirty sink.twenty one
Chicken is particularly susceptible to contamination
The type of food you take home also affects the risk of contamination. Chicken from concentrated feedlot operations (CAFOs) remains one of the most problematic foods, with approximately 1 in 25 packages of chicken in grocery stores contaminated with salmonella.twenty two
In New Zealand, Michael Baker, a public health researcher and professor at the University of Otago, has urged the implementation of “tobacco-style” warning labels on all raw chicken products to inform shoppers of the health risks involved. “It’s the most dangerous thing you can bring into your kitchen,” he said.twenty three
Recent research has also conclusively proven that most urinary tract infections (UTIs) are actually caused by exposure to contaminated chicken.twenty four Simply put, the E. coli bacteria that cause UTIs can enter your body through the food you eat (i.e., CAFO chicken, pork, and beef).
One study involved 2,460 chicken, pork and turkey samples purchased from a large retail store in Flagstaff, Arizona, and nearly 80 percent were found to contain E. coli.25 The researchers also tested blood and urine samples from patients attending a major medical center in the region and found that 72.4% of people diagnosed with urinary tract infections had E. coli in their systems.
Washing your hands may help
To reduce the risk of cross-contamination in the kitchen, simple hand washing goes a long way. Research shows that people who try to wash their hands or complete more steps to wash their hands can significantly reduce the risk of cross-contamination.26 Even washing your hands for 5 to 8.99 seconds can significantly reduce the risk.
In light of the results of this special study, you’ll also want to wash your spice containers thoroughly – and avoid handling raw chicken if you’ve just handled them. However, resist the urge to buy antibacterial cleaners, as these products can contribute to the development of antibiotic resistance. Instead, use natural cleaners to clean your kitchen.
Oregano oil is one such product that has natural antibacterial effects on human tissue and kitchen countertops. In one study,27 Researchers found oregano oil to be effective against three gram-negative bacteria and two gram-positive bacteria. Adding oregano essential oil to homemade cleaning products is a simple, easy, and effective way to kill pathogens without risking your health.