Salmonella in Tomatoes

So I have been working hard at writing a lecture I am giving next week as part of our continuing education series and I totally missed the latest food scare of Salmonella in raw tomatoes until a friend just asked about it. I’m writing about Food Science for the Non Food Scientist and I totally missed this story. Hits head with hand and groans.

Unripe Tomato on the vine

Raw tomatoes, especially raw Roma, have been implicated in an outbreak of Salmonella Saintpaul, which seems to be a particularly nasty version of Salmonella. Before you stop eating tomatoes NOW be aware that many types are not implicated in this outbreak. From the FDA:

The following types of tomatoes listed below are NOT likely to be the source of this outbreak.

  • cherry tomatoes
  • grape tomatoes
  • tomatoes sold with the vine still attached
  • tomatoes grown at home

The FDA also lists states from which tomatoes have been grown and harvested which are NOT associated with the outbreak.

One of my friends asked me for the solution and I said cooking the tomato would solve most of the problems. It seems that the FDA does not agree with me and recommends throwing away suspect tomatoes. There have been 12 outbreaks since 1990 that were associated with tomatoes, making up 17% of produce outbreaks.

It is interesting to consider where the problem might occur. Obviously, contamination can occur at anytime during the growing and processing of tomatoes, but how are fresh tomatoes processed?

Well, forget your ideas from home grown tomatoes. Most tomatoes grown commercially are determinate varieties which means all the fruit ripen at the same time. So the harvest can be fully mechanized – there is a mechanized harvester which cuts down the plant and shakes it to get the tomatoes to fall off. These are then sent to the processing plant where they are washed, graded and then stored at quite a high temp to prevent damage and poor flavor development. Some tomatoes are grown using a hydroponic system, which means that they are mineral rich solution instead of in soil.

It is still not clear whether Salmonella ended up inside the tomato, like E.coli O157 H7 did with the spinach. While for spinach, this was an clue to the source of contamination (cultivation water supply), the same cannot be said in this case as fruit such as tomatoes continue to take up water through the stem scar even after harvest.

Looking up for more information I came across this interesting blog: “Barfblog: Musings from the International Food Safety Network” where they have daily updates about the recent tomato scare. I have added it to my blogroll for future reference.