Speaking of pressure canning, I think it is something that everyone should learn how to do if they are going to can at home. It’s like learning how to dress yourself but stopping with shirts because the zippers are just so darn complicated and dangerous. Nonsense! If you can turn your stove on and boil water you’ll have no trouble with pressure canning. Nowadays, it is very unlikely and extremely hard to turn your pressure canner into a bomb. In my experience, it’s much more likely that you’ll have more trouble getting it up to pressure (newbies are shyer about turning up the heat and getting that steam formed).
But why pressure can at all? Most fruit and veggies are perfectly fine to water-bath can. That’s true, but there is a whole other low-acid world out there waiting to be stuffed into jars and preserved! All meat, including stock, veggies like green beans, corn, and some tomato products and some fruits like Asian pears must be pressure canned to be safe.
If there is only one product that should make you eager to go out and buy a pressure canner it would be chicken stock. Homemade chicken stock has changed my life. Pan sauces taste richer and more complex, soups and stews are heartier, and it adds a whole new dimension of flavor when used a poaching broth. Sure, you can freeze homemade stock, but if you’re anything like me, when you need it the most its frozen solid. It is so much more convenient to have liquid chicken stock ready and waiting on the shelf when I need it.
Because I am a microbiologist by training, here is a bit of science behind pressure canning versus water-bath canning. The biggest food safety concern when home canning is botulism, Clostridium botulinum, to be exact (my great-grandfather actually died of this in 1928 from improperly preserved fish). Botulism is a bacterium that can live in the soil but the toxic portion of it is actually the spores it produces. It’s a clever little organism for producing spores in the first place; spores are much more common in fungus and much less so in bacteria. Spores are able to hang around in inhospitable environments for long periods of time and then when conditions are just right spring back into action as bacteria. As you can imagine, they’re incredibly hard to kill. It is their job is to be virtually indestructible. Worse yet, they are also odorless and tasteless even after sitting and proliferating in your improperly preserved jars of food. But don’t worry, they are not invincible, they actually have two soft spots in their armor—acid and heat.
The acid content in most fruits is sufficient to halt botulism spores and especially recipes that specifically call for it in the form of vinegar or lemon juice. This is also why it’s incredibly important to follow canning recipes exactly as they are written. It’s not a good idea (unless you really, really know what you’re doing or call your extension service’s preserving hotline) to tweak canning recipes by omitting or altering the ratio of ingredients, especially if a recipe contains a mix of high and low acid foods. However, when canning low-acid foods like corn, for example, you must pressure can them. The temperature of a water-bath canner maxes out at the boiling point of water 212 degrees Fahrenheit. Because of the pressure, temperatures in a pressure canner can reach 240 degrees Fahrenheit, which are sufficient for safe and sterile food.
If it sounds scary and complicated, it’s really not. If you follow directions, you’ll be safe and rewarded for your efforts with preserved tasty treats. Here is a great resource to learn more about both types of canning. https://www.fcs.uga.edu/ext/food/nchfp_elc/ It’s a self-guided, online course all about canning. It’s great if you are brand-new to canning or just need a refresher if you haven’t done it in a while. I have done it and the best part is you get to print out a certificate at the end, which made me feel special. Another great resource is the Ball Blue Book Guide to Canning. It can usually be found seasonally at stores like Fred Meyer, Wal-Mart, Target, and any time of year online. It’s around $10.00 and is a great primer with pictures and recipes for both water-bath and pressure canning. Perhaps the best resource is your local extension service. Locally, a lovely group of Master Food Preservers regularly offer seasonal classes on cooking, baking, and canning. Hands-on experience is often the best way to learn and my assignment for you is to see if your county has a local extension service that offers classes like these. I promise you won’t regret it!
PS: I have not been paid in any shape or form to recommend these resources. They are just 3 sources I have personally found invaluable and recommend.