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Pressure canning is the process in which sterilized hot or raw packed food is brought to a pressure equal to two atmospheres. One atmosphere is the environment you are currently sitting in reading this post. This is why different altitudes require different pounds of pressure as different altitudes are effectively at different pressures. The closer to sea level you are, the more pressure you’re under because the air is more dense and the reverse is true of higher altitudes.
Using heat and a pressurized environment, achieving two atmospheres of pressure increases the water temperature to 250 degrees. The reason for this? To remove two obstacles from the equation of successful food preservation. Microbes and oxygen. Creating a vacuum in the jars increases the shelf life of the food but it isn’t without its hazards. The temperatures in question will destroy the bugs that will spoil the food if they are maintained for the correct amount of time based on the size of the vessel. The larger the vessel the more time it takes for the heat to penetrate all the way through the food. The denser the food in the jar, the longer processing times will be or it will not be recommended to home can the food in question. If these times are ignored, the environment becomes conducive to the grow of botulism spores. These spores are the big baddies that cause paralysis and in extreme cases, this can lead to death.
Botulism is a soil born spore. Foods that are low in acid are most susceptible to the growth of botulism if they are processed incorrectly. This is why it is so very important to follow the guidelines found in The Ball Blue Book and other publications that follow the scientific principals of home canning. If the food in question has a pH of 4.6 or lower, its generally safe to water bath can. Anything higher than that and into the pressure canner it must go.
https://www.exploratorium.edu/cooking/icooks/10-02_article.html
https://www.bernardin.ca/en/sciencebehindheatprocessing.htm
https://www.americastestkitchen.com/articles/329-foolproof-preserving-the-science-of-canning -
Great information! Thanks for sharing it. I’ll add – low acid foods like meat and vegetables must ALWAYS be pressure canned. It doesn’t matter if your grandma water bath canned beef and vegetable soup for 4 hours and nobody died. It’s simply too risky and we have safer options now.
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I’ve been canning meat for many years. A proper canner is a necessity. Mine holds 7 quarts or 16 pints. And do always follow all the rules about time and temperature depending on the particular food. Such a convenience to have on hand in the winter, when particularly poor,or suddenly have guests.
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For what it’s worth comment: Some pressure canners work well as pressure cookers. During the recent tropical storm that passed through SC, NC and VA, our power was out for five days. My intent was to cook a pot roast in the crock pot before the power went out. I was able to cook the 3 lb roast, carrots, onions and ‘taters on the gas range in approximately 40 minutes. Even though we have a backup generator, I don’t like to use electricity to heat stuff – other than the coffee pot first thing in the morning. I don’t have the patience or the ability to use the pour over before my first few cups.
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Well, my niece and here husband was here for Christmas this year. She has now retired and this spring she is coming over for me to teach her how to can food. It will be fun. She said she used to watch her grandmother do it but she never really paid attention or really learn how to do it as a child. So I will be teaching her this summer. I was really glad she wants to learn. Now if I could get my daughter to learn. Her husband wants to do it but she keeps saying she’s scared of the pressure cooker. I am not buying that one. I have used a pressure canning from the time she was still in diapers. Have been canning for years. So I can’t figure her out. Told her to let her husband do the canning and she do the prepping. She seemed good on that part. Now to get him over here to learn the canning process.
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AnonymousI water bath can, so what’s the main difference between that and pressure canning? Just the time needed?
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No. As stated above you must pressure can low acid foods (meat, or anything with meat in it).
I have a Graniteware pressure canner (20qt) but the jar rack always rusts. I was wondering if anyone knows where I can get a stainless or chrome jar rack. If not which canner do you use?
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Dala, I got an extra rack on Amazon (aluminum, in my case). Since I have a Presto pressure canner and don’t trust the dial gauge, I also got a 3-piece jiggler weight for it, and it’s been wonderful using it!
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Thanks Jeanne! Will start scouring for a new one.
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