When do You Need a Pressure Canner?

Written by: Lindsay Evans • Edited by: Donna Cosmato
Updated Jul 6, 2011 • Related Guides: Recipes

If you like to preserve food at home, it is important to note which foods can be safely processed with a water bath canner and which foods require a pressure canner. Learn why low-acid foods like vegetables and meat can only be safely processed using a pressure canner.

Pressure Canning vs Water Bath

To safely can any food at home you need to be sure to kill any microorganisms, such as mold or bacteria, during processing.

A water bath canner is perfectly safe to use for processing foods that are high in acid. Foods that are considered high-acid are those with a pH level below 4.6. Acidic foods include fruits, most tomatoes, and pickled foods. The acidic environment inside the jars of high-acid foods is not a favorable environment for bacteria and microorganisms to multiply.

Some potentially harmful microorganisms are not destroyed at the temperature inside a boiling water canner. For instance, the bacteria that can produce botulism toxin is destroyed at 240 degrees F, well above the temperature at which water boils (212 degrees F). Furthermore, the conditions inside a jar of low-acid canned goods is precisely the environment in which botulism toxin can flourish. Botulism is a serious toxin that can cause paralysis or even death.

Considering the potentially dangerous consequences, it is imperative to use a pressure canner to preserve any low-acid food as well as follow a tested and approved recipe. Pumpkin, is an example of a low-acid food that must be canned with a pressure canner. Do not be tempted to experiment with your own recipes or make substitutions to approved recipes. Doing so may alter the pH of the finished food, therefore making it unsafe to can.

Using a Pressure Canner

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Pressure canners are easy to use once you learn the necessary steps to follow. Always follow the instructions accompanying your pressure canner. If you do not have the instructions that came with your canner or have never used a pressure canner before, call your local Agricultural Extension office for an appointment to have your pressure canner tested. Someone should be able to help you inspect the canner's gasket and pressure gauge to ensure they are working properly.

Two kinds of pressure canners are available, weighted gauge canners and dial gauge canners. Weighted gauge canners come with a weight that is designed to jiggle or rock a few times a minute when the correct pressure is obtained. Dial gauge canners will display the current pressure inside the canner on an easy-to-read dial. Both types of pressure canners are safe to use, given that you follow the instructions.

Pressure canners must vent steam for 10 minutes after the canner is filled and the lid is locked. This necessary step eliminates the air in the canner, making it possible for temperatures inside the canner to climb high enough for safe processing. After venting, place the weighted gauge on the canner and wait for the gauge to read the appropriate pressure called for in your recipe. Once the correct pressure is obtained you can begin the processing time for your recipe.

Note that instructions in recipes are for canning at or below 1,000 feet in elevation. To safely can foods at higher elevations, you must add additional pressure. Again, follow your canner's instructions or call your local Agricultural Extension office.

Read on for instruction on how to get started canning at home. For additional information on using pressure canners, visit the National Center for Home Food Preservation.

Lindsay Evans Nov 2, 2009 12:21 PM

why take the risk?

Jason,
Here are some resources for you about botulism and home canning:
From Ohio State University Extension Fact Sheet, "There are very few cases of botulism each year. The death rate is high if not treated immediately. Prevention is extremely important. Home canning should follow strict hygienic recommendations to reduce risks. Pressure canners should be used for all low-acid foods. In addition, home-canned foods should be boiled for 20 minutes before eating. The botulism spores can only be killed by the high heat which can be obtained in a pressure canner. The toxin (that is produced in anaerobic conditions) can only be destroyed by boiling."
Also see the scientific article (available online) "Foodborne Botulism in the United States, 1900-2000" by Jeremy Sobel et. al, The article was published in the journal Emerging Infectious Diseases, vol. 10, no. 9, September, 2004.

Jason Oct 30, 2009 9:36 PM

How did we ever survive

So, canning has been around for over 100 years. Obviously back then, the main canning process would have been heat, and not steam, as if it were around, it would have been way too expensive.
How did we all survive canning meat (beef and pork) and other low acid foods? I mean surely there must have been some approved recipe... Or some magic trick, lost in the ages.
Out of all the thousands or hundreds of thousands of families that canned over the years, there's been no mentions of mass illnesses with countless families across the continent.
My family, as well as thousands of others have all done it in the past. If it was so dangerous, wouldn't there be accounts of illnesses somewhere.
In this day and age, it seems like pressure canning is just a precaution. If I knew any better, I'd almost think the industry created the demand for the pressure canners through fear mongering.
Like nuclear energy in reverse... Where the newer energy source, according to all the coke (coal) and electric companies was going to blow up the entire globe, as it was so volitile and unsafe.
Really, are the odds of botulism that high? Has there been that many hundreds or thousands of confimed cases linked to heat canning to say that it's not worth it? Or is it just a precautionary thing, or is it like everything else in society today fear mongering?
I'd love to know. I'd love someone to be completely honest. But chances of that happening in the sue crazy world, will most likely never happen.
But I'd really like to know what the odds are. Sounds like a person could win a super lottery and get struck by lightning twice in one day before getting botulism from heat canning, as long as you use common sense and follow directions. After all, as I said, they've been doing it in the past for decades.

When do You Need a Pressure Canner?

Pressure Canning vs Water Bath

Using a Pressure Canner

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