Academic warns that washing fruit and veges in dishwasher is not a good idea due to dirt, chemicals and germs

Washing fruits and vegetables helps remove dirt and debris and reduce potential pathogens. Photo / Getty Images

Washing fruits and vegetables helps remove dirt and debris and reduce potential pathogens, but a dishwasher might not be the best method for this task.

The question:

Is it true that you can wash fruits and vegetables in the dishwasher?

The science:

Social media is awash with a viral food prep hack - using the dishwasher to clean raw produce from the garden or grocery store. TikTokers suggest it saves them time and energy, particularly when washing large amounts of produce.

Washing fruits and vegetables helps remove dirt and debris and reduce potential pathogens, food safety experts say. But a dishwasher isn’t the best method for this task. And though it typically does not pose a health risk, it may have the opposite outcome.

“You can do more harm than good by washing produce in the dishwasher,” said Kathy Savoie, professor and food safety expert at the University of Maine Co-operative Extension.

The Food and Drug Administration does not recommend using kitchen appliances such as dishwashers to wash produce.

Dishwashers use detergent and other chemical agents, along with hot water that can reach more than 68C, to clean dishes, experts said.

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Social media users point out that they use only the rinse cycle with cool water and no detergent.

Dishwasher models vary, and at least some use cool water with the rinse cycle option, which circulates clean water throughout the dishwasher. However, even when detergent isn’t added to the dishwasher, the appliance may contain residual detergents and rinse aids, experts said. (Some rinse aid dispensers hold enough rinse aid for many cycles and release a certain amount during each rinse.)

Additionally, dishwashers can harbour bacteria, moulds and yeasts that may be transferred onto fruits and vegetables, some experts explained. Or some of the fruits and vegetables themselves may have micro-organisms growing on them, such as mould, and because dishwashers recirculate the water, those spores may be transferred to the rest of the produce. Although most micro-organisms are not likely to be harmful, they can lead to spoilage, experts said.

Dishwashers use hot water, detergents and other chemical agents to clean dishes, but they aren't always clean themselves. Photo / Getty Images

“Washing produce in the dishwasher is an opportunity to introduce microbes versus getting rid of microbes, which is the ultimate goal of washing it,” Savoie said.

What else you should know:

From farm to table, fruits and vegetables can become contaminated with listeria, E. coli, salmonella, as well as viruses, including hepatitis A and norovirus, said Benjamin Chapman, department head of agricultural and human sciences at North Carolina State University.

To help remove these and other pathogens, as well as dirt and debris, thoroughly rinse produce with cool, clean, flowing water from the kitchen faucet, food safety experts recommend. But beyond that, Chapman said, the dishwasher is not going to remove more pathogens than tap water, and running tap water is more effective because it carries away bacteria and viruses rather than recirculating them.

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Here’s what experts suggest:

• Wash your hands and then your produce in a clean and sanitised kitchen sink, allowing cool water to flow over fruits and vegetables. Wash them right before you plan to consume them, not in advance as water can encourage microbial growth that can lead to premature spoilage.
• Use a vegetable brush on thick-skinned produce such as carrots to remove dirt and debris.
• Place small or fragile items such as berries in a colander and let the water run over them.
• Soak produce with nooks and crannies in clean, cool water for a couple of minutes before rinsing. (Do not soak berries as they tend to absorb water.) In a 2006 study, researchers inoculated apples, broccoli, lettuce and tomatoes with listeria and found that soaking the apples, lettuce and tomatoes in water before rinsing significantly reduced the number of bacteria on the produce, but pre-soaking was not as effective for broccoli. They also found that soaking the lettuce in lemon or vinegar solutions was not significantly different from soaking it in plain water.
• Once clean, dry produce before storing it. A salad spinner can be an effective tool for removing excess water. But for fragile items, simply place them on paper towels to dry them. “Water is the enemy of fruits and vegetables when you’re storing them,” said Luke LaBorde, a professor of food science at Pennsylvania State University.

The bottom line:

Washing produce in the dishwasher typically does not pose a health risk, but it is not as effective as using cool, running water from the tap.