In a recent observational study conducted by the US Department of Agriculture (USDA), 383 volunteers agreed to prepare a meal of turkey burgers and salad at specially designed test kitchens, where their every step would be monitored.
To measure the spread of potential contamination in a kitchen, the raw burgers were laced with an RNA virus called bacteriophage MS2 – harmless to humans, this virus can be used to simulate the spread of more nasty pathogens, such as the noroviruses that lead to food poisoning.
The study wasn’t about hand-washing, though. After splitting the volunteers into a ‘control’ and ‘treatment’ group, researchers compared people’s cooking behaviour depending on whether they watched an instructional food safety video on how to measure the safe internal temperature of cooked meat.
After recording the entire cooking and cleaning session, the team also noticed alarming departures from proper hand-washing practices – 97 percent of the participants didn’t include all the handwashing steps recommended by the Centers for Disease Control and Prevention (CDC).
Here are those steps: wet your hands, lather up with soap, scrub your hands for at least 20 seconds, rinse the hands, and dry them either using a clean towel or by air drying.
According to the study, both the control group and treatment group overwhelmingly – an average of 79.5 percent – failed to scrub their hands for at least 20 seconds. Many of them also didn’t wet their hands before lathering up, and didn’t dry their hands properly after rinsing.
Since the researchers collected microbial samples from around the kitchen to see where MS2 from the raw meat ended up, the contamination from these lax hand-washing attitudes became bleedingly obvious.
Nearly half of the people in the control group contaminated the spice containers they used when preparing burgers, and 11 percent also contaminated refrigerator handles and water taps.
Most disturbingly, 5 percent of the control group managed to carry the virus from the meat patties to the salad lettuce about to be served with the meal.
“This rate of contamination of the salad indicates that cross-contamination was not necessarily frequent but did occur with some regularity, which could be a significant area of concern when extrapolated nationally,” the researchers wrote in a summary of their report.
As for meat thermometer use, people in the group who watched the video were twice as likely to use a thermometer and to insert it in the correct location of the patty (from the side, in case you’re wondering). And 66 percent of them said the video influenced their cooking behaviour.
But even if you manage to cook your food to a “safe internal temperature”, that’s little use to your family who ends up eating tainted salad because you didn’t wash your hands.
Since CDC data shows around 128,000 Americans get hospitalised due to foodborne illnesses every year, we’re guessing the USDA is already producing their next instructional video.
“You can’t see, smell or feel bacteria,” says USDA spokesperson Carmen Rottenberg.
“By simply washing your hands properly, you can protect your family and prevent that bacteria from contaminating your food and key areas in your kitchen.”
Of course, the vast majority of microbes kicking around our environments are totally fine, so there’s no need to panic and go full-on germaphobe in your kitchen – just use common sense and properly wash your hands with soap and water.
You can read the executive summary of USDA’s study here.