Botulism strikes soup-eaters; do current labels really work?

I was never really much of a soup fan until a few years ago. My stance was that it seemed to be a lot of work for a little pay-off (in the form of food calories and taste). I was much more interested in eating cheeseburgers and fries. But after expanding my eating habits (and reducing my cheeseburger consumption) butternut squash and apple soup has become one of my go-to recipes. A couple of times I’ve grabbed a prepared, chilled soup at retail for convenience (cutting up all the butternut squash is a pain) but have been pretty disappointed with the flavors.

The soups must be popular; they take up lots of real estate in the take-home/reheat meal or produce aisles. Many of the soups are low acid, provided in vacuum-packs or jars (no oxygen) and if not held cold would be a great environment for C. botulinum toxin production.

Tragically, that is what appears to have happened to two individuals early this year.

U.S. CDC reports in MMWR that a 29-year-old man in Ohio and a 41-year-old woman in Georgia had both eaten a commercially produced potato soup that had been purchased from retailers with refrigerated cases and labeled (in 1/8 inch tall text) "keep refrigerated" both developed botulism symptoms.

According to MMWR,

On January 28, 2011, an Ohio resident, aged 29 years, was hospitalized after 5 days of progressive dizziness, blurred vision, dysphagia, and difficulty breathing. The patient required mechanical ventilation and botulism antitoxin. On January 18, he had tasted potato soup from a bulging plastic container, noted a bad taste, and discarded the remainder. The soup had been purchased on December 7, 2010, from the refrigerated section of a local grocer, but it had been kept unrefrigerated for 42 days. He was hospitalized for 57 days and then was transferred with residual weakness to a rehabilitation facility.

On April 8, 2011, a Georgia resident, aged 41 years, was hospitalized after 4 days of progressive dizziness and dysphagia. The patient developed respiratory distress, required mechanical ventilation, and was treated with botulism antitoxin. On April 3, she had tasted potato soup purchased from a local grocer, noted a sour taste, and discarded the remainder. The soup, stored in a plastic container labeled "keep refrigerated" in letters 1/8 inch tall, had been purchased on March 16, but had been left unrefrigerated for 18 days. She was hospitalized for 16 days and then was transferred with residual weakness to a rehabilitation facility.

In September 2006, six folks in GA, FL and Ontario (that’s in Canada) developed botulism that was eventually traced to commercially-approved carrot juice. One of the individuals died 90 days after illness onset. One year later, two others were still on ventilators.

In 2008, carrot juice outbreak investigators wrote in Clinical Infectious Diseases "This investigation demonstrates that carrot juice and other processed foods with no natural barriers to C. botulinum germination require additional chemical or thermal barriers." The change-in-process suggestion is echoed by the potato soup investigators: "To inhibit the growth of C. botulinum and other microbes, an acidifying agent or other microbial inhibitor, such as citric or phosphoric acid, can be added to prepared, chilled foods before they are sealed in a package."

Investigators didn’t blame consumers for not following directions. It’s tough to blame folks on ventilators when the risks associated with improper handling aren’t  discussed in clear terms. Many point to people in their kitchens or check-out lanes as an important link in the food safety chain — and they are — but we need to do a better job in discussion risks and control measures. "Enjoy after heating" or "Keep refrigerated" probably aren’t all that effective. Not a lot of behavior data to back it up (because not much has been done), but there are lots of illnesses from products with poor labels (see: pot pies, frozen pizzas, frozen chicken thingies, cookie dough).

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About Ben Chapman

Dr. Ben Chapman is a professor and food safety extension specialist at North Carolina State University. As a teenager, a Saturday afternoon viewing of the classic cable movie, Outbreak, sparked his interest in pathogens and public health. With the goal of less foodborne illness, his group designs, implements, and evaluates food safety strategies, messages, and media from farm-to-fork. Through reality-based research, Chapman investigates behaviors and creates interventions aimed at amateur and professional food handlers, managers, and organizational decision-makers; the gate keepers of safe food. Ben co-hosts a biweekly podcast called Food Safety Talk and tries to further engage folks online through Instagram, Twitter, Facebook, YouTube and, maybe not surprisingly, Pinterest. Follow on Twitter @benjaminchapman.