While food preservation is a priority for me, my confidence in canning safely prohibits me from venturing too far into this particular method of putting up food for the winter.
My caution about canning is that I might poison my family via botulism.
If you aren’t familiar with botulism (Clostridium botulinum), it is a bacterium that produces toxins under low oxygen, low acid, low salt and sugar conditions. The toxin affects the nervous system and can cause respiratory failure, if left untreated.
The bacterium itself is not dangerous to humans. It is the spores the bacterium grows when under stress that germinate and produce toxins.
Foodborne botulism is my primary concern, as it is a controllable situation. But there is also wound, inhalation and injection botulism. The bacteria are ubiquitous in soil and aquatic sediment. They produce eight distinct toxins, four of which are harmful to humans.
It can be lethal, hence my fear of canning anything with low acidity (green beans, mushrooms, etc). In food, botulism spores and toxins are invisible and odorless.
Even products with moderate acidity I’ve hesitated on, telling myself I won’t can salsa or pasta sauce and such without getting acidity test strips to be sure the recipes produce a pH of less than 4.5.
While canning tomatoes recently, I wondered if all this fear was founded. People have been canning and preserving food in various ways for centuries. Did many of them really die of botulism?
I remembered reading that botulism poisoning can be treated, if caught early enough.
Even with my excessive caution in canning, I figured knowing the symptoms would be very useful — in case accidentally I serve something containing the toxin.
The toxin first impacts cranial nerves, causing symmetrical palsies, proceeding to flaccid paralysis. Symptoms include blurred vision, dry mouth and throat, drooping eyes and face muscles. It can also cause abdominal swelling, digestive issues and respiratory issues or failure.
An antitoxin can be given to those with botulism poisoning, but that only stops further damage — my understanding is that it does not reverse damage. Mechanical ventilation can help those who have had the damage progress to their airways.
While learning about botulism, I picked up a few interesting tidbits. The first, and probably most important, is that the toxin is killed by maintaining a heat of 185 degrees for at least five minutes. Canned food cooked in this way is therefore safe.
Another is a reference I read to a virus that infects the bacterium being the cause of botulism toxicity. I didn’t find more information on this, as most sources focus on the dangers of botulism.
While botulism toxins are apparently among the most toxic substances known, it does not poison everyone.
However, because botulism is so toxic and can be attached to aerosols, the military and CDC have been concerned that it could be used as a bioweapon. According to a paper abstract on the NIH National Library of Medicine website, the CDC has been working on a vaccine for botulism.
The problem with this vaccine though is another interesting twist — since FDA approval in 1989 botulinum toxin has been effectively used in some medicines in treatment of numerous neuromuscular, autonomic and sensory disorders. The vaccine would render these medications ineffective.
After learning more about botulism, I am still proceeding with caution when canning, but am glad to now know more specifically what I fear.
