Botulism & Unsafe Canning Methods - PVP29

Show Notes

Botulism is no joke! I understand that some folks might decide to not home can because of the real dangers. I do not want to replace or supplant good information--so please learn about botulism on the Center for Disease Control (CDC) website: Botulism: General Information and Frequently Asked Questions.

Recent Cases of Botulism and What Went Wrong

Three outbreaks of Type A botulism occurred in Ohio and Washington in September 2008, January 2009, and June 2009. Home-canned vegetables (green beans, green bean and carrot blend, and asparagus) served at family meals were confirmed as the source of each outbreak. In each instance, home canners did not follow canning instructions, did not use pressure cookers, ignored signs of food spoilage, and were unaware of the risk of botulism from consuming improperly preserved vegetables. Home-canned vegetables remain a leading cause of foodborne botulism. These outbreaks illustrate critical areas of concern in current home canning and food preparation knowledge and practices. Similar gaps were identified in a 2005 national survey of U.S. adults. Botulism prevention efforts should include targeted educational outreach to home canners.
— J Food Prot. 2011 Dec;74(12):2090-6. doi: 10.4315/0362-028X.JFP-11-128.
 red baron peaches. great fresh or great as jam! Photo credit:

red baron peaches. great fresh or great as jam! Photo credit:

A more recent case in Ohio in June 2015 involved home canned potatoes. Home canned potatoes were served at a potluck in a potato salad. That sounds scary! So, what happened?

The home preserver used a water bath canner instead of a pressure canner to can potatoes. A water bath canner isn't a substitute for a pressure canner. Ever. Why? A water bath canner is cannot reach the temperatures required to create a safe, shelf stable food as it can only process food to the temperature of boiling water. In contrast, a pressure canner can process food to temperatures of 240 degrees or higher. The higher temperature kills the cooties that cause illness and death.

Once upon a time folks thought that extending water bath canning time would be a suitable substitute for the high temperatures in a pressure canner. Okay, that seems reasonable. But, how much time would that be? Twice as long? Three times as long? Nope, 7 to 10 hours! Of course, there are no food safety scientists developing recipes for safe water bath canning with times like that!

Home-canned vegetables are the most common cause of botulism outbreaks in the United States. From 1996 to 2008, there were 116 outbreaks of foodborne botulism reported to CDC. Of the 48 outbreaks that were caused by home-prepared foods, 18 outbreaks, or 38%, were from home-canned vegetables. These outbreaks often occur because home canners did not follow canning instructions, did not use pressure canners, ignored signs of food spoilage, and were unaware of the risk of botulism from improperly preserving vegetables.
— Center for Disease Control,

Bottom Line

Never, ever substitute a water bath canner for a pressure canner. And when in doubt, toss it out!

Oven Canning

From 1931 to 1942 the USDA gave its stamp of approval to oven canning. In 1944 the USDA issued a warning against oven canning. Here's the deal: oven canning involves dry heat. Dry heat doesn't penetrate the jars and the food in the same why as moist heat. Okay, so? Well, that means that the cooties that cause illness and death are not going to be killed during oven canning. Plus, there are zero, zilch, no guidelines for oven canning. Plus, jars may crack and explode. In other words there are no data to support home canning in an oven. Yes, we could go on about what if scenarios--but the bottom line is no current research, no current guidance, thus no safe recipes for home canning in the oven. 

Microwave Canning & Dishwasher Canning

Microwave canning and dishwasher canning. Both of these just make me go, huh? Why do we insist on innovating in the kitchen? It isn't the same as cooking a roast in the oven or on the stove top or in the microwave or in a crock pot. The underlying problem with both of these methods are: heat penetration to kill the cooties just isn't present or consistent. There are no tested methods or recipes using a microwave or dishwasher for home canning.

Canning Powders 

Canning powders are interesting to me--I wonder how we arrived at thinking this might be a good idea. Canning powders could be labeled "Not Safe Since 1917". Yup, a century ago scientists determined that canning powders had a minuscule if any affect on controlling the growth of microorganisms as part of canning. Canning powders contained boric acid, salicylic acid, and salts or a combination of one or more ingredients. Interesting but completely not safe. Like so many things we people "rediscover" an idea and run with it--in this case, don't!

Open Kettle Canning

Oh gosh, the jam and jelly purists are going to be upset. Bottom line here is that cooties are simply not excluded using the open kettle process. I recommend eating that wonderful, delicate jam today and storing the leftovers in the fridge. 

And finally, if the boredom or curiosity is sweeping over you, can delve into all the gory details of the history of home canning by reading Critical Review of Home Preservation Literature and Current Research. The lead author, Elizabeth Andress, is also one of the authors of a reliable canning book: So Easy to Preserve available from the University of Georgia. Penny up $18.00 for a terrific book full of safe recipes and good information!

Be safe and eat well.


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