I recently asked our Facebook Group, Garden Fundamentals, what they used for washing fruits and vegetables and I got quite a range of answers. Some did not wash most items. Quite a few used just water and many used a type of soap. Vinegar and baking soda were also popular for washing fruits and vegetables.
What does the science say about different washing solutions for fruits and vegetables?
Why Wash Fruits and Vegetables?
I can think of several reasons including, dirt, pesticides and germs.
Washing the Dirt Off
Produce from the store is usually fairly clean but not if it is from your garden. Dirt makes things taste bad and may contain germs. Washing the dirt off makes sense.
Getting Rid of Pesticides
It seems as if pesticides are a big concern and a main reason for washing produce. Gardeners wash their own home grown fruits and vegetables less than store bought, mostly because they assume their own has fewer pesticides.
Some things to know.
- Most of the pesticides in and on produce are natural pesticides. In fact 99.9% are natural. The amount of man-made pesticides is so small that it does not cause a health risk – so there is not much reason to wash them off.
- It is very hard to remove natural pesticides because most of these are inside the fruits and vegetables.
- A lot of the synthetic pesticides are water-soluble and will come off easily with water.
Psychologically, washing pesticides off seems to be important, but practically speaking it is not an issue to worry about.
Washing Off Germs
In the last few years there have been regular recalls of vegetables due to pathogen contamination, such as Salmonella, E. coli, and Listeria. This is a real concern.
Fruit and vegetables are handled by many people before they get to your kitchen and at each stage they can be contaminated.
Is Homegrown Produce Safe?
Your home grown produce has been handled by fewer hands, but it can still be contaminated by soil pathogens. It should be washed.
How Effective are Commercial Washes?
The Department of Food Science and Human Nutrition at the University of Maine tested three commercial wash treatments and found that for both residual pesticides and microbes, distilled water worked as well as, or better than, the commercial products.
Another study tested four commercial products on a variety of fruits and vegetables to measure their effectiveness at removing pesticides. They also tried plain tap water and a 1% solution of Palmolive dish detergent. Tap water was just as effective as the other washes.
Commercial washes are expensive and are no more effective than tap water.
Vinegar for Washing Fruits and Vegetables
Vinegar is a very common DIY vegetable wash and instructions go something like this: add 1 cup of vinegar in a sink of water and soak fruit for 10 minutes. This leads to confusion about its effectiveness because government sources usually suggest a much stronger mixture, something like a 3:1 ratio of water to vinegar. Why is this important? The effectiveness of vinegar depends very much on how diluted it is.
Household vinegar is about 5% acetic acid. If you dilute it in a 3:1 ratio you have a 1.25% solution. One cup in a sink of water is closer to a 0.1% solution.
A study that looked at the effectiveness of vinegar looked at the microbial load on five different vegetables with a vinegar concentration of 0.5 to 2.5%. A 0.5% reduced the microbes by 15%, but a 2.5% solution reduced them by 82% (10 minute soak). A cup of vinegar in a sink of water is not any better than water alone.
Washing Fruits and Vegetables With Soap
The US Department of Agriculture has this to say, “Consumers should not wash fruits and vegetables with detergent, soap or commercial produce washes. These products are not approved or labeled by the U.S. Food and Drug Administration (FDA) for use on foods. You could ingest residues from soap or detergent absorbed on the produce and get sick.”
Soap does kill germs (see note below) and we are advised to wash our hands and working surfaces with soap to sterilize them. If that is safe, why not wash produce with soap? Counter tops and hands are not permeable, produce is. That means fruits and vegetables absorb the chemicals in soap, hands don’t. Eating soap can cause irritation to your gastrointestinal system, leading to vomiting or diarrhea, and it could interfere with your gut microbiome. Even the material safety data sheet for Dawn dish detergent says “Ingestion may result in nausea, vomiting, and/or diarrhea”.
Update: I had written that soap kills germs, but that is not correct. We wash with soap to get the germs off our hands, but it does not kill them.
Washing Fruits and Vegetables With Bleach
Bleach is commonly used for killing germs so it has also been suggested for cleaning produce.
One study compared running tap water (for 15 seconds) to a bleach soak of 2 minutes and found that bleach does reduce the bacterial level better than water, especially on vegetables that are hard to clean with running water, such as broccoli and cantaloupes. The bleach solution was prepared with 5 ml household bleach (6% sodium hypochlorite, Clorox) in 3.785 L (one gallon) of water to produce a 70 ppm free chlorine solution.
The chlorine in bleach will absorb into produce so a soak should be short. It should also be washed off with water after the soak. The CDC does NOT recommend the use of bleach for washing fruits and vegetables. US federal regulations (21 CFR Part 173) say the concentration should be less than 2,000 ppm and the produce must be rinsed in water afterwards. Most produce does not need more than 200 ppm.
Washing Fruits and Vegetables With Baking Soda
When a baking soda wash was compared to water, for cleaning Chinese kale and Pakchoi of two common pesticides, chlorpyrifos and cypermethrin, baking soda was more effective for one pesticide but equal to water for the other.
Water, bleach and baking soda were tested on apples to measure their ability to remove pesticide residues. Baking soda worked best. however they found “that 20% of applied thiabendazole and 4.4% of applied phosmet had penetrated into the apples following the 24 hour exposure” and none of the washes removed the absorbed pesticides.
Baking soda is as effective as vinegar for killing bacteria, but neither is as good as other products including bleach and ethanol. Another study looking at the antimicrobial properties of so-called “green” solutions, vinegar, baking soda, borax and ammonia, found that they were not very effective compared to commercial disinfectants, for cleaning nonporous surfaces.
Washing Fruits and Vegetables with Peroxide
Hydrogen peroxide has antimicrobial properties and has been suggested by some. The problem with peroxide is that it quickly changes to oxygen and water, and that is just what a study found when they tried to wash leafy vegetables with it – they could not keep a high enough level of peroxide in the wash water. It was less effective than water.
Best Way to Wash Produce
People use various means for cleaning produce but as you can see, none of the methods are much better than cold tap water and some can even be harmful. Health and food safety experts, including the Food and Drug Administration (FDA) and Centers for Disease Control (CDC), strongly urge consumers to stick with plain water. It is just as effective as other DIY concoctions and commercial washing products. Water removes 90 to 99% of what is on produce.
How should you wash your fruits and vegetables. The FDA has a good guide, but here are some important points.
- Wash your hands with soap before washing and preparing produce.
- Wash produce even if you plan to remove the peel. Simply slicing through the peel can transfer germs onto the edible parts.
- Rise under running cold water for 20 seconds.
- A scrub brush works well on harder surfaces.
Keep things simple. There is no point in using household chemicals on your fruits and vegetables.