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Ask Dr. Gourmet

Can produce carry COVID-19?

How should I clean my produce? I am worried about Covid19 and whether food might act as a carrier for the virus. I have seen suggestions for dilute vinegar, bleach and hydrogen peroxide solutions. What do you suggest?

Dr. Gourmet Says...

washing lettuce in a green plastic bowl

I don't think that I would be overly concerned, personally - as long as I washed my produce. It appears that there is a possibility that the virus could survive on produce. Other viruses are transmitted this way - one of the most common is norovirus, for example - but it appears coronaviruses are less likely to be a problem.

To answer your question directly, here are the FDA guidelines about COVID-19. The info is at the bottom of the page in the Food section.

As we here at Dr. Gourmet always do, this does recommend washing produce and here is the page on washing your produce: 4 Steps to Food Safety.

Now, on to the question of whether transmission is possible. Interestingly, there has been research on the Survival of Respiratory Viruses on Fresh Produce (journal article).

It appears that we are at less risk of transmission, with the amount of coronavirus found to survive on produce much lower than other respiratory viruses (that is very reassuring). The authors note:

"CoV229E was very sensitive to the elution process. The recovery efficiencies were low, with no virus recovered from strawberries and only 19.6% recovered from lettuce. In addition, the CoV229E fell to below the detection limit of our assay within 4 days of storage at 4°C. These results are comparable with those obtained by Gundy et al. (2009) who reported that coronaviruses die-off very rapidly in wastewater."

There has not been good evidence that washing with more than just water will help all that much. Using water that has some acid might help, but it appears to be a minor improvement. Here is one of the reviews that I have relied on for years — related mostly to enteric viruses (the ones that cause gastroenteritis): Foodborne viruses and fresh produce.

An excerpt from Section 8 indicates that washing in water is likely sufficient, although reading all of section 8 says that water with some acid might be a bit superior:

Most fruit and vegetable washing systems are designed to remove gross contamination such as dirt, insects, and foreign matter. However, they are reported to be less successful at removing microbial contaminants (17114). Vigorous washing of fruits and vegetables with clean potable water typically reduces the number of micro‐organisms by 10–100‐fold (17) and is often as effective as treatment with 100 mg l−1 chlorine, the current industry standard (37114). Raw materials are typically immersed in cooled sanitized water and then dewatered to remove surface moisture and fruit and vegetable juices from the product (115). Product agitation is optimized by using water or air jets which enhance surface contact, carriage of product, and suspension of solids and vegetable debris (115). There has been recent concern over the possible migration of bacterial pathogens into the core tissue of fruits and vegetables during washing.130 found that uptake of bacterial cells was associated with a negative temperature differential between the water and the product. However, the uptake of human viruses by fruits and vegetables under similar conditions has not been studied. Lodging or attachment of microorganisms in tissue crevices may protect cells from direct contact with disinfectants and consequently aid in their survival (16). Recent studies by 113 found that Escherichia coli O157:H7 could survive in the stomata and on cut edges of lettuce following chlorine treatment. Although there are no available data for viruses, cell surface structures are likely to offer some additional protection.

In conclusion:

1. Do wash in tap water (as you should always do).

2. Dilute vinegar (acetic acid) in water may be superior and I would use it given that the vinegar is easily available. About 1/4 cup per gallon of water is more than enough.

Thanks for writing,

Timothy S. Harlan, MD, FACP, CCMS
Dr. Gourmet