If you don't wash the pre-washed spinach you buy from the store, you may want to stop reading. Actually, even if you do wash your spinach, you still may want to stop here. According to new findings by food safety researchers out of the University of California, Riverside, bacteria such as E. coli and salmonella can survive even the bleaching process used in food processing plants thanks to the many folds and contours in a typical spinach leaf. In fact, 15% of a typical spinach leaf sees itself exposed to only trace amounts of disinfectant. What remains can be much more than that: "Following rinsing under the low bleach condition, upwards of 90% of adhered bacteria were observed to remain attached to and survive on the leaf surface," per the university.
Unfortunately, once those bacteria are there, they tend to multiply and spread, reports Yahoo Health. Worse still, "Rinsing isn’t going to do a whole heck of a lot for food safety," says Benjamin Chapman, a food safety specialist at North Carolina State University. Indeed, a second food safety expert tells Yahoo Health he won't eat raw spinach because of the risks; the CDC estimates that about 17% of Americans become ill and 3,000 die every year from foodborne diseases. Chapman says that while at-home washing essentially just removes bits of dirt and debris, cooking the spinach does eliminate the bacteria. These findings, which have not yet been submitted for publication but were Thursday presented at the 250th American Chemical Society National Meeting & Exposition, have implications beyond spinach since many leafy greens have lots of grooves. (Researchers have called this the No. 1 powerhouse vegetable.)