The Final Word on Washing Chicken

Let's settle this once and for all.

The debate around “washing chicken” is one of those topics that just will not die. Every couple months, some well-meaning science enthusiast on Twitter will get riled up about how the whole point of cooking is to kill bacteria, so rinsing your chicken in the sink before cooking it is worse than useless: it can splash germs everywhere, so—the logic goes—you’re more likely to get sick than if you just took it out of the package and slapped it straight into the pan. The replies are usually full of comments like “smdh, y’all don’t even understand the point of washing it lol”, half of which seem designed to infuriate by refusing to elaborate or explain further.

Part of what makes this a perennially effective piece of engagement-bait is that there’s a weird racial element to the discourse: washing meat before cooking is often purported to be a “black people thing”. There’s a grain of truth to this, in that white people are more likely to be “non-washers” in the US—but on the whole, ~70% of Americans report that they do it.¹ Complicating the matter is the fact that people can mean a dozen different things when they say “wash”; most give their meat a quick rinse-and-rub under the tap, some use a lemon juice or vinegar solution, still others say it’s actually more like a brining process—and a few absolute madmen are apparently out there genuinely scrubbing their chicken breasts with a dollop of Dawn or other detergent.²

Now, I feel uniquely qualified to weigh in on this because in my lifetime I’ve been both a physicist and a microbiologist, and both of those domains have insight to offer here. The truth of the matter is that there are good reasons to rinse your meat before cooking—but you have to do it right.

But Cooking Kills Bacteria!

Sure. Unless they’re spore-formers.

In a previous post, we talked about the threat of Clostridium perfringens, a fast-growing bacterium that represents one of the most common causes of food poisoning. Most strains won’t give you anything worse than a case of the runs, but certain rare varieties also produce a toxin that destroys the myelin-producing cells in the brain, causing a syndrome that looks suspiciously like multiple sclerosis in animals. Suffice to say: it’s bad stuff and you don’t want it in your body—but it’s hard to avoid, because something like 80% of grocery store chicken samples test positive for C. perfringens.

The main reason that food poisoning caused by C. perfringens is so common is that the bacterium produces spores, which are like seeds for bacteria. A dried kernel of corn can survive a drought, a hard freeze, and a dozen other conditions that would kill the full-grown plant—and by the same token, bacterial spores are resistant to heat, acid, antibiotics, and most other methods of decontamination. This is why, when we’re making nutrient broth to grow bacteria in the lab, we use an autoclave: an industrial-strength pressure-cooker that can kill even the hardiest of spores. But recipes that call for pressure-cooked chicken are few and far between, so if you want to reduce your exposure to pathogenic spores, it’s hard to beat physically removing the bacteria from your food—and rinsing is a pretty effective way to do that.

It’s not perfect, of course, but it doesn’t need to be. Microbiologists often talk about pathogens in terms of the “ID50”—or “infectious dose for 50%”. You might have heard of the concept of “LD50” (or lethal dose - 50%) for toxic chemicals, e.g.: if you give 2mg of fentanyl to a group of 10 people, about 5 of them will die and 5 will survive. Similarly, the ID50 is the number of cells of a given bacterium you need to ingest for there to be a 50% chance of it making you sick. Anything that lowers your total exposure reduces the odds that you’ll get a dose that’s too much for your immune system to handle. Infectiousness depends on more than pure numbers, though: bacteria are also a lot better at surviving stomach acid and causing disease when they’re in the form of a biofilm—effectively a layer of slime made from their secretions. Gently rubbing a piece of meat while running it under the tap is usually enough to wash that slime down the drain, taking most of the bacteria with it.

Stable vs. Labile

Things like Salmonella and E. coli don’t produce spores, but spores aren’t the only nasty bacterial byproducts that can withstand cooking: there’s also heat-stable toxins to worry about.

When microbiologists talk about toxins, it’s not in the nebulous, woo-adjacent sense that can supposedly be addressed with a “detoxifying” juice cleanse. Bacterial toxins are proteins that microbes produce in order to wreak havoc on your cells, and they’re usually the main thing responsible for the symptoms of disease. Cholera toxin, for example, works by forcing your intestinal cells to spew out water and salts into the GI tract—resulting in the watery diarrhea that gives the microbe a great chance of getting into a new host.

But cholera toxin is what we call heat-labile: cooking denatures it, effectively removing its toxic properties, so it’s only a problem if you get a live colony of the organism in your body. In contrast, E. coli can produce heat-stable enterotoxins which retain their ability to give you the shits even after being exposed to common cooking temperatures. It’s not as serious as an infection with the live bacterium, where the toxin factory sets up shop in your intestines…but if your chicken has been sitting in the cooler long enough to grow a biofilm, there’s a chance that the slime contains enough heat-stable enterotoxin to cause some serious (albeit temporary) GI distress—even if you kill all the bacteria that produced it.

But Washing Splashes Bacteria!

Not if you use some goddamned common sense.

Yes, if you set a raw chicken breast in a colander at the bottom of the sink and turn the faucet on full, you will get “chickensplash”. The same is true if you blast it with the sprayer-nozzle: the amount of rebound you get depends pretty heavily on how fast the water is moving when it hits the surface of the meat. We know this for a fact, thanks to some physicists who tested splash under various conditions, and found that faucet height and water pressure were the primary factors determining how far contaminants spread.

But when you actually look at how people act in the kitchen, this starts to look like a much less serious problem than it’s made out to be. In 2019, the USDA published the results of a remarkably thorough study, where they had real people come into a test-kitchen and prepare a meal the way they would at home, using chicken thighs inoculated with a harmless “tracer” bacterium. They also had participants prepare a salad, and checked both the salad and the kitchen surfaces for contamination with the tracer bacterium, allowing a comparison of contamination rates between chicken-washers and non-washers.

The result? When real people wash chicken, the bacteria generally don’t go much further than the sink. Even within a mere six inches of the sink’s edge, the tracer bacteria only showed up 20% of the time after people washed their chicken. 12 inches away, that number drops to 8%—and the counts of bacteria were so low as to be negligible. Curiously enough, while the salad was contaminated slightly more often for washers than for non-washers (25% vs. 20%), when non-washers’ salads did have the bacteria in them, there was seventy times as much as in washers’ salads. One potential explanation for this is that, if you’re washing your chicken, you’re more likely to be conscientious about washing your hands afterward—while a non-washer might forget to give their hands a good scrub between slicing the chicken and diving into salad prep.

Best Practices

All told, there are some good reasons to rinse your meat before you prep it, and—provided you do it right—you’re not very likely to create a contaminating cloud of bacterial mess. That’s as simple as keeping the water pressure on low or medium, holding the meat a few inches from the tap, and giving it a good rub-down. If you avoid letting ready-to-eat food touch the inner surface of the sink afterward (a no-brainer), you’re practically home free.

Of course, I don’t expect this post to truly settle anything; most people arguing on the internet seem to be more interested in feeling superior than in understanding or finding truth. But at the very least, I hope it provides some reassurance for those in the civilized majority who rinse their meat before cooking it: grandma knew what she was talking about.

—🖖🏼💩

1. Armchair anthropologists thus rationalize it as a practice held over from the days of slavery or something, practiced among those Superstitious and Uninformed Minorities who don’t know how to apply logic and modern knowledge to their daily lives. This is…not a great look.

2. I suspect this is troll behavior, engaged in to get outrage-shares; most dish soaps are so strongly scented that I don’t see how this wouldn’t ruin the food.