MINNEAPOLIS (WCCO) — We hear about E. Coli in spinach, listeria in celery, and salmonella in sprouts. And our best defense is something we as consumers have been doing for decades: running fruits and vegetables under water. But does washing produce really do anything?
“Rinsing at home is largely not very well understood,” said Dr. Francisco Diez-Gonzalez, a University of Minnesota associate professor who has studied the impact of various washing techniques on produce.
“At the consumer level, washing from the point of view of numbers, may reduce risk to 10 percent of the original risk. That’s been fairly consistent. But it’s definitely not solving the problem,” said Diez-Gonzalez.
According to Diez-Gonzalez, a lot of this is about luck.
“If you happen to be lucky and the cells of the pathogen are not going to be attached to the surface, you may get lucky. If the cells have formed some structure and are strongly attached to the surface, you may not,” he said.
Washing with water and some scrubbing motion applies friction, which has been shown to dramatically reduce the number of bacteria on a fruit or vegetable — from 100 percent risk to 10 percent risk, for example. But when the original numbers are in the trillions, that 10 percent risk can still be significant.
“You can reduce the number, but you’re not gonna get zero,” said Dr. Ted Labuza, Diez-Gonzalez’ colleague at the University of Minnesota. “If there’s one organism, it still can cause food poisoning.”
The studies show a range of results depending on technique. Rubbing an apple on a shirt does work, according to the University of Tennessee, reducing the number of bacteria, but not to the extent that washing does. Running water on a fruit can reduce the risk to 15 percent. Scrubbing gets you to 10 percent, and using a mix of 3 parts water, 1 part vinegar can reduce the risk to 1 or 2 perecent.
So, it’s doing something, but it may not be enough.
There is good news, according to Diez-Gonzalez.
“The risk isn’t tremendous. And not all fresh vegetables and fruits are the same. There are a few that have been linked to outbreaks of food-borne disease,” he said.
Consider: “cucumbers may have never been linked to a food-borne outbreak. Carrots: almost never. Onions: same thing,” said Diez-Gonzalez.
When you think of the most potential for food-borne illness, the worst vegetables are the hardest to wash. Alfalfa sprouts have been linked to salmonella and E. coli, and leafy lettuce has also had troubles. Neither of those categories is easy to wash.