Home Canning: What about Botulism?

I had planned to write a post about botulism next month, when I get more into canning low acid foods. Due to comments and e-mails from people that are afraid of poisoning somebody, I decided to move up the date.

Of all the unwanted organisms that might live on your food, the Clostridium Botulinum bacteria has to be the scariest. You can't see it; you can't smell it; and you can't taste it; yet it can kill you. Talk about scary.

So how do you protect yourself?


Once again, I will divide foods into two categories, high acid foods (food with PH below 4.6 such as pickles and most fruits) and low acid foods (food with a PH above 4.6 such as vegetables and meats).


High Acid Foods

For high acid foods, my discussion is short. Clostridium Botulinum will not grow in these food. If you have been afraid to can these foods, for fear of botulism poisoning; relax, breath a sigh of relief, and start canning. Just remember, that while bacteria will not grow in these foods, mold and other fungi will, so be sure to process your food in boiling water for the length of time specified in the recipe. The heat from the boiling water is necessary to destroy mold.

Low Acid Foods


Now we get into a discussion of why I keep emphasizing that low acid foods need to be processed in a Pressure Canner. The reason I go into details of what can go wrong is not to scare new people away from canning, but to give you enough information that you are prepared to can food safely.

Let's say you pick some green beans from your garden or buy some ears of corn from the farmers market. This food is bound to have dormant spores of the Clostridium Botulinum bacteria on it. These spores are so common that their presence is inevitable. The reason why they are in their dormant state is because they need a low oxygen environment. As long as they are exposed to air, they must remain in their dormant state.

Even after you wash your food, some of these dormant spores will remain on the food. It is nearly impossible to wash them all off. Fortunately eating these dormant spores, does us no harm. You eat the all them time, you just never knew it.

Now let's say that you decide to can this food. Let's also say that for whatever reason, you did not process it at the proper pressure for the proper length of time to ensure that all the spores are destroyed.

Now you sit your jar of food on the shelf to eat later. These spores are now sitting in a cool, moist, low oxygen, low acid environment. This is just the environment they have been waiting for. They come out of their dormant state and start actively growing. As the bacteria grows, it release a chemical that is toxic to humans. In as little as 3 days, your jar of food will be poisonous.


OK, I Know That I Need To Use A Pressure Canner, But I Am Still Scared.

Now let's say that you were very careful to process the food at the specified pressure for the specified length of time, but you are still worried that one of those spores might have some how survived. How can you tell?

The bacteria doesn’t discolor your food, or cause a funny odor, but it does still give its presence away. As it grows, it releases a gas which loosens the seal on your jar. In a properly sealed jar, you should need a jar opener to get the lid off. You should not be able to pull it off with your fingers. Any jar with a loose seal, should be considered contaminated.

As I said before, the reason I wrote this is not to scare people away from home canning, but to encourage people to practice safe canning. A lot of research has been done over the years. We now know much more than we once did about what canning techniques are safe and what techniques are not safe. If you take advantage of what has been learned, home canning can be a very rewarding experience.