Salmonella and tomatoes? A food safety expert answers your questions.

Tomatoes with stems are OK, says the Leigh Ann Hubbard, managing editor

When our publisher James Hubbard, M.D., M.P.H., wrote about the tomato/salmonella outbreak this week, blog reader “Deborah in Chicago” asked some fantastic questions about it. “I’ve read several articles…and look at how many questions I have!!” she wrote. We took that as a challenge.

Sam Beattie, Ph.D., assistant professor of food science and human nutrition at Iowa State University, was kind enough to participate in an e-mail interview on short notice. Here are his answers to what we assume are some frequently asked, though not answered, questions about this outbreak.

JHMFD: Deborah has heard the salmonella is from people relieving themselves in the tomato fields. Is this true?

SB: Humans are included in the reservoirs of Salmonella, however, it is much more likely that a wild animal was the source. Fecal material deposited into the field by birds, snakes, wild boars, and almost any other animal could contain enough Salmonella to cause an outbreak.

JHMFD: Once salmonella is on one plant, can it grow and spread to others? How does an outbreak happen?

SB: Salmonella is not likely to grow on or in a plant, it is more likely to be a passive contaminant just sitting on or in the plant. What is more likely is that a heavily contaminated bit of soil or tomato was transferred into the wash water. This caused the water to become contaminated and served as a Salmonella source for the rest of the tomatoes. Alternatively, a contaminated water source for the spray irrigation system could also contaminate a large number of tomatoes.

JHMFD: How could salmonella get inside a tomato?

SB: Salmonella can get inside of a tomato by damage but most likely because of a temperature differential during the washing and cooling with water processes. A large, 10 degrees or more differential, may cause contaminated wash water to be drawn into the tomato. Salmonella and any other microorganism in the water will be drawn into the tomato through the stem scar. While other fruits/vegetables may exhibit a similar trait, the producers try to minimize the differential as much as is possible.

JHMFD: Why would a difference in temperature do that?

SB: A temperature differential (fruit warmer than the wash water) will cause the tomato to draw water into the fruit. As it does so, Salmonella will be carried into the internal portion of the tomato.

JHMFD: Won’t washing the tomato off make it safe?

SB: Salmonella could get onto the tomato through spray irrigation or sprinkler irrigation using contaminated water. Research has shown that once a bacterium contacts a vegetable or fruit surface it is extremely difficult to remove. Normally washing helps a bit but there still may be enough to make people sick. The critical control is use uncontaminated water or a different type (drip or other) irrigation system.

JHMFD: Deborah asks, ” I soak all my veggies in vinegar and salt…this is supposed to kill ecoli…wouldn’t it also kill salmonell??”

SB: There are a variety of different vegetable washes available on the consumer market. Some are effective at removing a portion of the bacteria but not all. The use of vinegar (a mild acid) and salt will likely rinse off some bacteria but is not likely to kill many. The use of these washes may not be effective at even reaching the bacteria that may be present inside the fruit or vegetable.

JHMFD: Do you think the washes are worth spending money on?

SB: The washes are good for people who believe they need a bit of extra protection. Washing produce under running water with scrubbing removes soil and bacteria also.

JHMFD: Is there anything else you think needs to be covered?

SB: This is an unfortunate outbreak and one that has consumers very concerned about eating tomatoes. Fruits and vegetables are a very important source of nutrients so daily consumption should be high. The current outbreak in tomatoes involves tomatoes from a specific growing region. Tomatoes from other growing regions and locally grown ones should be safe and should continue to be consumed.


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9 Responses to “Salmonella and tomatoes? A food safety expert answers your questions.”

  1. Mark Salinas Says:

    Very important information in this article. There are so many questions and uncertainties, it is reassuring to have a reliable resource to refer to. I am going to start a garden next year. I miss my tomatoes! Excellent detail..thank you!

    Mark Salinass last blog post..Foam Roller for Prevention and Recovery

  2. lhubbard Says:

    Thank you, Mark. I’m glad you found it helpful. Mmmm … home-grown tomatoes …

    Leigh Ann Hubbard
    Managing Editor
    James Hubbard’s My Family Doctor

  3. Jessica Says:

    Thank you for shedding some lights on the outbreak issue.I never thought eating veggies could make people sick.

    Jessicas last blog post..How To Prevent Cancer

  4. James Hubbard, M.D., M.P.H Says:

    Thanks Jessica, from your website I can see that you know that fruit and vegetables are a great way to help prevent cancer. I hope no one stops eating these just because of the latest scare. I know I look forward to an end to the warnings so that I can go back to eating tomatoes.

  5. Yemek Tarifleri Says:

    Thanks about this for this reason it is so important for me. Thanks again :)

  6. Yemek Tarifleri Says:

    Thanks for this. You was help me. Article who your writen was so important for me. Thanks again :) I am reading all articles in happily

  7. tisort Says:


  8. Education Blog Says:

    Thanks for the informative post.. and thanks for adding our comment to the blog. I am subscribing to your feed so I don\’t miss the next post!

  9. James Hubbard’s My Family Doctor Blog » Blog Archive » FDA salmonella update: could be tomatoes, could be peppers … the good news Says:

    [...] Salmonella and Tomatoes? A food safety expert answers your questions. [...]

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