Monday, January 14, 2008

Botulism is back

Botulism is back in the news. The US Food and Drug Administration has announced that a canning company in Michigan is recalling certain lots of canned beans. The reason given was that these particular batches of product were not adequately heated during the processing.

As I wrote in “Deadly Poison in the Kitchen” on 5th September last year, the testing of canned foods for Clostridium botulinum is impractical. No sampling plan could detect the very low level of faulty cans that we accept. We are therefore totally reliant on the correct delivery of the thermal process by the manufacturer. Not surprisingly, the regulations covering the processing of Low Acid Canned Foods* are tight and specific.

The cans must be heated in a pressurized vessel called a retort at temperatures greater than 100C (the temperature of boiling water) because the C. botulinum spores are very heat resistant. They can survive for longer than 4 hours in boiling water. Full records must be made of the process, using special controllers and monitoring instruments. The retort operator must sign these records as soon as the cooking process is completed and they must be inspected and signed off by a responsible member of Management within 24 hours.

I don’t know the details of the investigation, other than the information provided in the FDA announcement ( However, it does appear that the procedures mentioned above were not followed. The FDA announcement, quoting the company, stated that the recall was made “because a records review identified the possibility that a small number of cans from each lot may not have been adequately cooked”. These cans should not have entered the distribution network until after the processing records had been inspected.

For the benefit of anyone who has concerns about the hazards of handling foods thought to be contaminated with the toxin (botulin) I have quoted the FDA release verbatim below:

“Any food that may be contaminated should be disposed of carefully. Even tiny amounts of toxins ingested, inhaled, or absorbed through the eye or a break in the skin can cause serious illness. Skin contact should be avoided as much as possible, and the hands should be washed immediately after handling the food. Customers who have the product or any foods made with these products should throw them away immediately. Double bag the cans in plastic bags that are tightly closed, then place in a trash receptacle for non-recyclable trash outside of the home. Restaurants and institutions are encouraged to assure that such products are only placed in locked receptacles which are not accessible to the public. Additional instructions for safe disposal can be found at Anyone with questions can call FDA at 1-888-SAFEFOOD”.

* A Low Acid Canned Food (LACF) is defined as a food packed in an hermetically sealed container, whose finished equilibrium pH is greater than 4.6 This includes, but is not limited to foods like canned beans, peas, carrots, corn etc. It is not safe to try to make these products at home and industrial production must be conducted in approved premises, using processes approved by thermal processing experts and filed with the authority (in the US this will be either FDA or USDA; in New Zealand it is NZFSA).

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