Home Canning & Botulism: A Taboo Topic

     I’d like to preface this article by saying there are no canning practices judgments here. My intent is to enlighten you about a topic you may not completely understand. I believe it is important to understand the rationale and science behind certain food preservation practices. A lot of us who homestead also preserve our own food using home canning as one method.
     Before we go any further, I want to make sure we are all on the same page. Canning can be classified into two categories: water bath and pressure canning. In simplistic terms, I’ve given definitions for both, basic recommendations and a picture for reference.
Water Bath Canner     Water Bath Canner 
A pot with a lid and jar rack containing boiling water in which food in separate jars are processed. Maximum temperature reached, 212°. Water bath canning is the recommended method to be used for high acid foods such as: pickles, jams, jellies & fruit butters, and most tomato products.
     Pressure Canner Pressure Canner
A special pot that is used to process food by using the pressure of steam. Maximum temperature reached, 250°. Pressure canning is the recommended method to be used for low acid foods including: vegetables, meats, poultry, fish, and other food items.
[Note: ° temperatures are given in Fahrenheit.]
     Ok, now that we are all at the same starting point. There are three types of botulism poisoning. For the purposes of this article I will only address the food borne.
Botulism     We encounter botulism spores daily. They are present in the soil, marine sediments and on most fresh food surfaces. The spores themselves are harmless, they only become deadly when certain conditions are met.
     First we have to understand what is required for the botulism spores to grow and produce their deadly toxin. Only two things need be present. 1) Temperatures of 239° or less and 2) an oxygen free environment such as sealed canned food jars. Botulism spores can only grow in the absence of air.
     Water bath canning at 212° degrees will kill most yeast, mold, and bacteria’s, but is ineffective at killing the botulism spores. Water boils and turns to steam at 212°. It can not get any hotter unless it is placed under pressure, regardless of how long it is boiled.
     [As a side note] We all know that water boils at 212°, but what many of us don’t realize is that water boils at lower temperatures the higher the elevation or altitude. For each 500 ft. increase in altitude causes a drop of about 1° in the boiling point. Examples: at an elevation of 1000 ft., water boils at 210° and at 2000 ft., it boils at 208°, and etc.
     So using the process time for canning food at sea level may not be killing all the nasty’s, resulting in spoilage if you live at altitudes over 1000 ft. This problem can be overcome by increasing the process time of your water bath or the pressure at which you are processing with using your pressure canner.
     Most of us are not sure of the exact elevation that we live at. Here is a link where you can type in your address to find out. http://veloroutes.org/elevation/
     Botulism spores can grow and thrive in an oxygen free environment within hours, ideally and optimally at temperatures between 70° and 110°, in product that includes more than 35% moisture. Temperatures below freezing, as well as moisture levels below 35%  render botulism spores inactive, which is why it isn’t a concern with frozen and dehydrated foods.

There is no home test to determine if jars contain botulism or not. The toxin is odorless and tasteless. Ideally, it would be best to pressure can all low acid foods to drastically eliminate the possibility of botulism contamination.

     However, there is a common practice in other countries that haven’t the knowledge or access to pressure canner’s. It is to reheat the water bathed, canned food for a minimum of 15 minutes at a  hard rolling boil. This will most likely kill any botulism toxic that may have occurred.
     I hope I’ve helped to inform you of some things you may not have known. What you do with it is up to you. I follow the doctrine of, your house, your rules.
Onward in Strength,
Mary Lotus

4 thoughts on “Home Canning & Botulism: A Taboo Topic

    1. Luckily for us home canners, pressure canners were extensively redesigned beginning in the 1970’s. It is almost unheard of these days for a canner to explode and if they do, it’s because of negligence on the humans part and/or not following instructions. Canners today, are super safe. The National Center for Home Food Processing and Preservation has free guides explaining all the ends and outs of canning. This is the link to their guide #1 of seven total to canning,. It’s full of all kinds of great information. http://nchfp.uga.edu/publications/usda/GUIDE01_HomeCan_rev0715.pdf


  1. Very good presentation. Minor bit of semantics. The 15 minute hard boil after opening doesn’t “kill” the toxin as the toxin isn’t a living thing, just the results of one. The boiling “deactivates/destroys” the toxin rendering it harmless.
    And modern pressure canners don’t blow up unless someone has welded all the safeties. They can blow the over pressure plug and scare the bejeebers out of anyone near by, but that even takes some doing.

    Liked by 1 person

  2. There is something I don’t understand here. The boiling for 15 minutes to kill the Spores? If they are not killed in a water bath canner, as it only reaches 212 degrees then why boil the canned food, which will only reach… 212 degrees and turn to Mush? I understand for possibly other pathogens , but if you have pressure canned something at 240 degrees it can’t survive, Right? And if you water bath canned it at 212 degrees, no matter how long, what difference will it make to rebuild it, again, at 212 Degrees? Don’t understand this. Please help me to.

    Liked by 1 person

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