Wednesday, December 9, 2009

Slim-Fast® Recall: The Unanswered Questions

On December 3, 2009, Unilever announced a recall of all flavors and production lots of Slim-Fast® Ready-To-Drink (RTD) products. The news wires are filled with regurgitations of the Unilever/FDA news release. But the information that is contained in the recall notice leaves some questions unanswered.

Two days ago, I sent Unilever a list of questions, in order to better understand the health hazard associated with the recalled Slim-Fast® RTD products. While waiting for a reply, I've been doing some digging on my own.

Based on what I've uncovered, I suspect that the health risk may go far beyond the chance of an upset tummy that would be associated with the Bacillus cereus contamination reported by Unilever. Here's why.

  • I found several Slim-Fast Ready-To-Drink ingredient lists on the National Institutes of Health (NIH) website. There are no preservatives in Slim-Fast RTD beverages.
  • Slim-Fast RTD beverages rely on an Ultra-High Temperature (UHT) pasteurization process, followed by an aseptic filling procedure (i.e., filling sterile cans under sterile conditions) to ensure product safety and stability at room temperature.
  • UHT pasteurization temperatures (at least 250ºF for a fraction of a second) should be far more than is needed to kill Bacillus cereus spores.

If Unilever found Bacillus cereus in a sealed can of Slim-Fast RTD beverage, that means one or more of the following likely happened:
  1. The UHT pasteurizer failed to reach the necessary temperature; or
  2. An ingredient of the formula (perhaps the milk powder) contained an unusually high number of Bacillus cereus spores; or
  3. A cross-connection in the pipes allowed unpasteurized product to contaminate the UHT pasteurized beverage; or
  4. The filling line was contaminated; or
  5. The packaging material was contaminated.

It's clear from the scope of the product recall that this is not a one-shot problem. Whatever conditions enabled Bacillus cereus to contaminate Slim-Fast RTD beverages have been in force for a while.

Bacillus cereus is not an especially heat-resistant bacterium. It is killed by temperatures that will leave more heat-tolerant pathogens such as Clostridium botulinum laughing – and asking for more.

I don't know whether the levels of sugar in the Slim-Fast RTD formulas are high enough to prevent the growth of Clostridium botulinum, along with the production of its deadly toxin. Perhaps this weight-loss beverage is an inhospitable environment for bacterial growth. I certainly hope so!

Otherwise, Bacillus cereus might be the least of Unilever's worries.

Applied and Environmental Microbiology, Vol. 54, No. 3: pp. 699-702. 1988.
Journal of Food Protection, Vol. 60, No.5: pp. 544-547. 1997.
Journal of Food Protection, Vol. 63, No. 2: pp. 190–195. 2000.

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