How to wash chicken in the kitchen more safely, according to physics

Health experts recommend against washing chicken before cooking it because that can spread harmful bacteria. But if you’re among the nearly 70 percent of people who do, according to a survey of U.S. grocery shoppers, there are ways to make it safer.

Instead of admonishing people not to wash chicken, says mathematician Scott McCalla of Montana State University in Bozeman, the goal of a study published in the March Physics of Fluids was to “recommend how to do it safely, or more carefully.”

The researchers placed raw chicken under running faucets and monitored the spray of water and bacteria to nearby surfaces. The outcomes changed dramatically depending on a few factors.

The height of the faucet above the chicken had the largest effect. If the water fell 40 centimeters (about 16 inches) before hitting a chicken breast or thigh, the germs traveled farther than for faucets just 15 centimeters (about 6 inches) above the chicken.

In tests involving the higher faucets, droplets of water splashed more than 22 centimeters in the air, contaminating much of the surrounding area. For lower faucets, droplets splashed only about 5 centimeters high, and there was comparatively little sign of contamination making it to nearby surfaces.  

The researchers also found that if they flicked on a faucet, the initial burst of water sent contaminated spray flying. Turning it on gradually reduced the spray. 

The pliability of chicken was also important. Water hitting the chicken creates a small divot in the soft surface, which shoots the splatter farther than it would if the chicken didn’t deform. Keeping the water pressure turned down reduces the dimpling and resulting germ spread. 

Raw chicken can be fouled by Salmonella and other bacteria that can cause foodborne illnesses (SN: 8/9/10). Even minor splashing will contaminate sinks with germs that can spread through contact with other foods and hands, says food safety researcher Ellen Shumaker of North Carolina State University in Raleigh, who wasn’t part of the study.

Reducing splashing, though, can still be part of what Shumaker describes as a multipronged approach to keeping germs in check in the kitchen. “We do know that there are always going to be people who always wash” poultry, she says.