Why are canned goods at high risk for botulism?

Question

What does the denting of the can have to do with it?
Is botulism already in the can or does the denting have something to do with it?

Answer 1

Clostridium Botulinum is an anaerobic bacteria that lives in soil (that is, it is a bacteria that thrives in the absence of air, specifically oxygen). If the can and contents are not properly sterilized (with high heat) before it is sealed, the bacteria will grow. The bacteria produces botulinum toxin, if you consume it, you get botulism. Cans bulge out when the bacteria grows, since it not only produces the toxin, it also produces gas. But it's not always enough to see. The key to keeping it from happening is proper sterilization. Dented can may not be a botulism risk, but they are subject to bacterial contamination, since the seal is broken, so all kinds of airborne bacteria and fungus can get in.

Answer 2

While commercially canned goods are required to undergo a "botulinum cook" (121°C for 3 minutes) and so rarely cause botulism, there have been notable exceptions (such as the 1978 Alaskan salmon outbreak). Foodborne botulism has more frequently been from home-canned foods with low acid content, such as carrot juice, asparagus, green beans, beets, and corn. However, outbreaks of botulism have resulted from more unusual sources. In July, 2002, fourteen Alaskans ate muktuk (whale meat) from a beached whale, and eight of them developed symptoms of botulism, two of them requiring mechanical ventilation [1]. Other origins of infection include garlic or herbs[4] stored covered in oil,[2] chile peppers, tomatoes [citation needed], improperly handled baked potatoes wrapped in aluminum foil [citation needed], and home-canned or fermented fish. Persons who do home canning should follow strict hygienic procedures to reduce contamination of foods.