Last week, University of Illinois professor Hao Feng unearthed some good news for green smoothie lovers. By combining continuous ultrasound treatment — yep, the technology doctors use to look at unborn babies — and chlorine, Feng discovered a way to rid spinach of 99.99 percent of pesky (and dangerous) E. coli bacteria.
Why It Matters
Healthy eaters have always crushed on spinach, the dark leafy superfood, for its nutritional benefits, but spinach has a checkered history in terms of public health. Greens like Popeye’s favorite food were responsible for 24 percent of food-related E. coli outbreaks between 1999 and 2009 and leafy greens are first on the FDA’s Riskiest Foods list. All field-grown veggies are at risk for contamination through contact with animal waste, infected irrigation or picking equipment, and even improperly fertilized soil. Lettuces like spinach are especially prone to contamination because they come into direct contact with soil and are usually eaten raw.
These days, rinsing leaves with a chlorine solution is the go-to technique for cleaning spinach before it hits the grocery shelves Efficacy of chlorine and acidified sodium chlorite on microbial population and quality changes of spinach leaves. Nei D, Choi JW, Bari ML, Kawasaki S, Kawamoto S, Inatsu Y. National Food Research Institute, Kannondai, Tsukuba, Japan. Foodborne Pathog Dis. 2009 Jun;6(5):541-6. . The chlorinated wash typically kills between 90 and 99 percent of bacteria, but some bacteria can still slip through and cause illness and even death to people with weakened immune systems, children, and the elderly Survival of Salmonella hadar after washing disinfection of minimally processed spinach. Pirovani ME, Guemes Dr, Di Pentima JH, Tessi MA. Instituto de Tecnología de Alimentos, Faculdad de Ingeniería Química, Universidad Nacional del Litoral, Santa Fe, Argentina. Lett Appl Microbiol. 200 Aug;31(2):143-8. .
As for the new cleaning technology, it's a lot less "science fiction" than it sounds. Ultrasound waves are just high-frequency sound waves that humans can’t hear. They’re best known as tools to check up on unborn babies or for diagnosing a wide variety of medical problems. But, believe it or not, ultrasound waves are also perfect for decontaminating food products like apple juice — and now spinach.
Can We Trust It?
Cleaning spinach is tricky because it’s delicate and disintegrates if zapped with too much ultrasound power. Too little oomph, and the leaves remain contaminated. Heng’s device looks like a big spinach-only hot tub with some special features. First he added a series of jets to keep the leaves moving through the tank so they were all continuously exposed to the same amount of chlorine solution and ultrasound waves. Next he inserted large ultrasound transducers into the tub so the waves would be evenly distributed. Each piece of spinach is treated exactly like the others, so there’s no danger of contamination from any one leaf.
Right now Heng’s super-sanitizer is still in trial form, so it’s not available for mass use yet. Fingers crossed that Heng’s technology takes off, so we can all enjoy healthy and, more importantly, safer spinach.
Do you thing Heng's invention will make eating leafy greens safer? Tell us in the comments below or tweet the author at @SophBreene.