Despite what you might have heard, there are only two safe methods of canning food. Neither is better than the other, but both are used only for certain types of food.
What foods do you want to can? Pickles, jams and jellies? Meat, vegetables and other low acid foods? The food you want to can will determine the processing method you need to use.
There are two SAFE canning methods. Just two.
Boiling Water Bath canning
This is perfectly safe for many foods – acidic tomatoes, fruit, jams, jellies, preserves and pickles.
This will get as hot as (drum roll, please) boiling water. A boiling water bath reaches a temperature of 212F at sea level. There is no way to make the temperature higher.
To process jars in a boiling water bath, the jars must be covered with at least 1″ of water and the processing time begins when the water is at a boil.
A pressure canner (which is different than a pressure cooker) opens up a whole range of possibilities and, surprisingly, it’s easier than BWB canning. Really. I tell people this all the time, but they don’t believe me.
You must pressure can all meats (including poultry and seafood) and vegetables – these are known as low-acid foods. A pressure canner will get as hot as 240F.
Now, why do we have to pressure can low-acid foods?
Well, there’s this nasty microorganism called Clostridium botulinum that grows well under certain conditions.
Botulism needs a high moisture, low oxygen, low acid, low sodium, warm environment. In other words, the inside of a canning jar full of low acid food. So when we can, we need to make sure that we introduce as little of the microorganism, and kill as much of it, as possible.
When Clostridium botulinum grows, it turns into botulism, one of the deadliest neurotoxins we know about.
It occurs rarely, but when it does occur, it is frequently fatal.
All food have a certain pH, making them either low acid or high acid. Low acid foods (those with a higher pH) MUST be pressure canned in order to kill Clostridium botulinum. High acid foods (those with a lower pH) can be processed in a boiling water bath canner.
Okay, so beyond Boiling Water Bath for high acid foods and Pressure Canning for low acid foods, there is what I call:
Crazy Ways People Try to Kill Themselves and Loved Ones
open kettle canning
canning in a dishwasher
Boiling Water Bath for meat, vegetables, cheese and milk
microwave canning (how is this a thing?)
adding aspirin to tomato and then sealing in a clean jar without processing
sealing jams and jellies with paraffin wax
using a pressure cooker to process jars of food
There’s no excuse to say “Oh, but open kettle canning was the proper and safe way when we were young,” unless you’re 80. And maybe not even then.
My copy of Putting Food By, published in 1974, addresses the issue that people are STILL open kettle canning despite twenty years of being told that it’s not safe.
In addition, my father tells me that my grandparents had a pressure canner in the 1940s and the government was extremely generous in providing pamphlets and information on how to safely (for the times) pressure can their meat and vegetables.
It truly isn’t a new thing.