(Editor's Note: This article was originally published on August 20, 2009. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
Home canning gives you a chance to preserve the bounty of your garden, orchard, or local farmers' market. With a boiling water bath canner, you can make delicious and unique pickles and jams. But what if you want to can vegetables, or soups, or sauces with oil or meat? Then you need a pressure canner.
I started thinking about a pressure canner when I realized how much freezer space I was taking up with little containers of roasted tomato sauce. The recipe includes olive oil, so processing in a boiling water bath isn't safe. I thought about my grandma's old rattling canner, though, and I worried that pressure canning might be just as dangerous. Not so! Modern canners are very safe, as long as you follow the manufacturer's simple guidelines. Yes, they still sound scary, as they whistle and rattle and steam. But a quick look at the gauge or pressure regulator will assure you that all is well.
If you're in the market for a pressure canner, here are a few things to think about. Some canners have pressure gauges. With others, you wait for a weight to jiggle when the pressure reaches a given number of pounds. A pressure gauge makes it easier to keep track of the process. Canners also differ in how their lids seal. Many models use a rubber gasket that must be periodically inspected and replaced if worn. Others, like my All American pressure canner, use a precisely machined edge rather than a gasket. Can you use a pressure cooker for canning? Maybe. A pressure cooker must be big enough to hold at least four quart jars in order to safely use it for pressure canning.
With a pressure canner, water is used to make steam but not to submerge the jars. Although an empty pressure canner is heavier than a water bath canner, they may weigh about the same when full. If your stove has a glass top, the manual will probably advise against using either type of canner on it. I decided to take the risk, but you may decide you'd rather can outside on a propane burner.
For safe processing, the canner needs a "venting" period, where air and steam escape at full blast for at least 10 minutes before you start the actual processing. Reaching that "full steam" stage can take longer than you might think. Don't set your timer when you start seeing little bits of steam escaping. Wait for a big, geyser-like plume of steam. The venting period is important for reaching the right processing temperature. If in doubt, let the canner vent a little longer. A few more minutes of cooking won't hurt the food.
Some foods are processed at a higher pressure than others, so check the chart to know how to set the counterweight on the valve. Once you've vented the canner, wait for it to reach the right pressure. You want to maintain the pressure without running the canner dry, so you'll need to turn down the heat. Those scary sounds as the valve releases extra steam are actually reassuring. The valve is just doing its job; the canner will not explode. When you see spurts of steam several times a minute, you're in the zone for perfect processing.
The first couple of times you use your canner, you'll need to pay close attention and fiddle with the heat a lot, especially on an electric stove. When you've found the setting that seems to work out well on your stove, it's a good idea to make a note of it. Pressure canning isn't really a "set it and forget it" sort of procedure. Even with experience, it's a good idea to check on the canner regularly during processing to make sure it's operating in the right pressure range. I like to sit where I can hear the regular "ppfftbbttt!" of pressure being released.
I'm an impatient cook, so for me the hardest part of pressure canning is waiting for the canner to cool down and depressurize before opening it. There's really no way to rush this stage. Go read a book, or explore a new DG forum. Do not run cold water over the canner or do anything else the manufacturer says not to do. If you really have to devote yourself to a marathon canning session, make a batch of jam and process it in a boiling water bath canner while waiting for your pressure canner to cool down.
Most of the time, when home cooks talk about "canning," they're really talking about putting things up in glass jars. But with a pressure canner, you also have the option of canning in actual metal cans. To me, it seems simpler to stick with my usual glass jars and two-piece lids. When filling jars, be sure to leave the recommended "head space" between the top of the contents and the rim of the jar. Don't worry if a little bit of liquid leaks out around the lid during processing. Check the seal, remove the ring band, and wash down the outside of the jar before putting it in your pantry.
Some things may need to be canned in a slightly different form than you'd find them on your grocery shelf. Pumpkin, for example, is unsafe to can as a puree (it's too thick and might not get hot enough in the center of the jar), so the chart will say to cut it into chunks for canning. It's wise to stick with "official" directions and recipes, in order to avoid potential safety problems.
Please follow all manufacturer's directions on a new canner. For additional information, or if you have an older canner, the University of Georgia Extension Service has an excellent website on home preserving, with an entire section on pressure canning procedures and recipes for canning vegetables and meats.
So, fear not! Pressure canning is simple and safe. I hope you'll give it a try and enjoy your garden goodies all winter long.
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For pressure canning the roasted tomato sauce mentioned above, I used the recommended processing time for "spaghetti sauce with meat" (60 minutes at 11 pounds with my canner, in half-pints). It's possible that a shorter processing time for "spaghetti sauce without meat" would be safe, but why take chances? Processing for the longer time will not hurt the flavor of the sauce.
Check out this upcoming article by Angela Carson for excellent instructions on pressure canning green beans!
My thanks to Darius and others for the great suggestions and encouragement posted in DG's Canning, Creezing and Drying forum.
Please note: The introductory information and tips in this article are NOT a substitute for thoroughly reading the manufacturer's information for your pressure canner.
Photos by Jill M. Nicolaus.