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.
clostridium-botulinum-toxin

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