What Is a Pressure Canner and How it Works
With the boom in popularity of pressure cooking using a multi-cooker such as the Instant Pot many people assume it can be used for canning, too (that’s understandable, those appliances have a lot of functions and pressure cooking is similar, just not quite the same.). But no, you cannot pressure can in a pressure cooker, only in a pressure canner. So what is a pressure canner? A pressure canner is a large pot that has a lid that locks onto the pot and a dial or weighted gauge that allows you to regulate steam pressure that builds up inside the pot by turning the burner heat up or down. The pressurized steam is much hotter than boiling water. It heats jars to 240°F to kill microorganisms in low-acid foods (a boiling water canner only heats to 212°F, which is not hot enough to destroy spores that cause botulism toxin). So, it is imperative you use a pressure canner when a recipe specifies it to keep food safe. Unlike boiling-water canners, you only put 2-3 inches of water into the bottom because you’re cooking with steam instead of boiling water.
Pressure Canner Regulators
On the top of all pressure canners is a dial or knoblike device called the pressure regulator. It helps you control the pressure inside the canner. There are three types of regulators:
Pressure Canning Step-by-Step
Once you’ve prepared your pressure-canning recipe, here’s how to pressure can your food safely.
1. Heat the Jars
Add 2 to 3 inches of water into the canner. With the lid loosely in place (not locked), bring water almost to a simmer (180°F). Put your jars into the pressure canner with just a little water in the jars to keep them from floating. Put the lid back on loosely and let the jars get steamy hot. After a few minutes, they’ll be ready to add food. Take one jar out, fill it, and replace it in the canner before removing another jar. Using a jar lifter is the safest way to remove and add jars to the pressure canner. Test Kitchen Tip: When filling any kind of canner, always remember one jar out, one jar in.
2. Fill the Jars
Fill one hot jar at a time; do not fill a cooled jar. Pack the food into the jar as tightly as you can without crushing it. Use a funnel, like the one in this Ball utensil set ($9.99, Bed Bath & Beyond) to keep jar rims clean. Top with the hot liquid as directed in your recipe. Measure the headspace and adjust as needed.
3. Remove Air Bubbles
Use a thin, flexible spatula to remove air bubbles by sliding the spatula between the jar and the food to release the trapped air. Add more hot water if needed for headspace.
4. Wipe Jar Rim and Add Lids
Wipe jar rim and threads with a clean cloth. Set lid in place and screw the band on fingertip tight. This is important so air can escape for a proper seal. Place the jar back in the canner before filling the next jar.
5. Fill the Canner and Lock the Lid
Set the last jar in place. The water in the canner should come up only a few inches and not cover the jars. Set the pressure canner lid in place and twist so the handles lock. Don’t add the regulator yet.
6. Vent the Pressure Canner
Turn heat to high and allow a full head of steam to come out of the vent pipe. Allow to vent for 10 minutes. For a weighted-gauge canner, adjust weights on the pressure regulator, if needed, and set the pressure regulator on the vent pipe to plug it.
7. Achieve the Correct Pressure
If the canner has a safety valve, it will pop from the down to the up position, showing the canner is pressurized. Do not open the canner. When the pressure regulator starts to rock, adjust the heat so it makes a steady rattling sound. Set the timer for the recipe-specified time (adjust for altitude, if necessary). For a dial-gauge canner, start timing when the gauge reads 11 pounds.
8. Depressurize and Open the Canner
When your recipe time is up, turn off the heat. Do not open lid. Wait until the safety valve drops back down or the dial returns to zero. This shows the canner is no longer pressurized and is safe to open. Remove the pressure regulator. Unlock the handles and open the canner away from you so any steam is directed away.
Cool the Jars
Allow jars to stand in the canner for 10 minutes to cool slightly. Remove them from the canner and set on a wire rack or kitchen towel. Do not tighten lids. Let cool 12 to 24 hours. Test seals by pressing on the lid (it should not pop up or down). Refrigerate any improperly sealed food to eat soon. Store the rest in a cool, dry place and try to use within one year. Use a permanent marker to note the date on the lid so you don’t keep canned foods longer than one year before eating.
Pressure Canning vs. Boiling-Water Canning
Pressure canners are used with low-acid foods prone to harboring harmful microorganisms. They heat food hotter than boiling-water canners to kill off the microorganisms. Low-acid foods are those with a pH over 4.6. Most vegetables, soups, stews, and meat sauces are low-acid. Unless a lot of an acidic ingredient (such as vinegar) is added, low-acid foods must be processed in the higher heat of a pressure canner. Boiling-water canners are basically big pots with a lid and a rack in the bottom. They’re used for high-acid foods, which naturally resist bacteria growth. High-acid foods have a pH of 4.6 or lower. Citrus juices and vinegar are very acidic. For that reason, most pickles and salsas are considered high-acid even though they may contain foods that are otherwise low-acid, such as green beans and beets.
