Pressure canner. Credit: Courtesy of Kate McCarty

Everyone knows someone with a canning horror story. More often than not, these stories come from watching parents or grandparents use a pressure canner.

Pressure canning is a high-temperature, high-pressure method for preserving foods.

“I feel like it does have an aura of intimidation,” Kate McCarty, food systems professional at the University of Maine Cooperative Extension, said. “A lot of people [who feel that way] witnessed someone in their family having a negative pressure canning experience [like] witnessing them explode. If you have that kind of negative impression, it might be time for an update.”

Even though its reputation isn’t wholly deserved, pressure canning is distinct from its popular counterpart, boiling water bath canning.

“The boiling water bath and pressure canner are two very different methods for preserving food,” said Kathleen Savoie, extension educator at the University of Maine Cooperative Extension. “A pressure canner reaches a higher temperature, over 240 degrees.”

Pressure canning opens up a new range of options in terms of what you can preserve, like meats or vegetables that have not been pickled.

“If you are canning the foods low acid, it’s not a matter of if you want to pressure can or not — you must pressure can,” Savoie said.

According to Savoie, low-acid environments allow the growth of botulinum spores into toxins, which can cause botulism, a potentially deadly foodborne illness. The high temperatures of pressure canning can kill the botulinum spore if it is present.

“There’s no safe way to process those foods in a boiling water bath,” Savoie said.

What equipment do you need to pressure can?

Modern pressure canning equipment has been updated to prevent some of the dangers of the bygone canning era.

“Today’s pressure canners have a lot of safety mechanisms built into them,” Savoie said. “They are much higher quality pieces of equipment than pressure canners of the past. They have over pressure plugs [and] built-in locking mechanisms.”

Pressure canners cost anywhere from $75 to a couple hundred dollars, depending on the size and features. Savoie said that a good pressure canner for beginners should cost between $80 to $120. Both McCarty and Savoie recommended purchasing a canner with a weighted gauge rather than a dial gauge. Dial gauge pressure canners need to be tested annually to make sure they are accurate, which can be done for free through the University of Maine Cooperative Extension.

Weighted gauge (left) versus the dial gauge (right). Credit: Courtesy of Kate McCarty

“The weighted gauge does not need to be tested annually to make sure it is accurate,” Savoie said.

Weighted gauges can also be easier to use.

“The weighted gauge is a lot easier to see that it’s at the proper pressure,” McCarty said. “[The weighted gauge] jiggles and makes a clackety noise when it’s at the proper pressure. The other is a dial with a needle on it, [so you] have to keep an eye on it.”

Home canners can also buy a used pressure canner if they thoroughly inspect it.

“Check the gasket on the underside of the lid,” Savoie said. “If the gasket looks dried up, that will need to be replaced. Make sure it has a rack [and] look to see if the handles are jiggly. You can get replacement parts if you know the model [which is usually on the] underside of the pot.”

Also, look for modern models that have the built-in safety features.

“If it looks like something that may have come from your grandmother’s pantry, you may want to make an investment in a newer model,” Savoie said.

McCarty said that you can also contact your local cooperative extension office to give your used pressure canner “the once over” and make sure it is in working shape.

McCarty and Savoie emphasized that electronic pre-programmable pressure cookers, like Instant Pots, are not safe for home canning. Aside from the fact that U.S. Department of Agriculture-approved canning recipes that have been tested for safety have not been tested with these products, the machines are regulated by a pressure sensor instead of a thermometer. Thus, the altitude of your location may affect the actual cooking temperature, and the contents of the material you are trying to pressure can may not reach the right temperature to kill botulinum spores.

“You really do need to have a pressure canner and not just a pressure cooker,” she said.

Aside from that pressure canner, you need the same basic equipment as with water bath canning: jars with screw bands and lids, a jar lifter, funnel and headspace tool.

How to pressure can

Savoie said that part of learning how to pressure can is to get familiar with the pressure canner you choose.

“I encourage people to always read the manual that comes with their pressure canner,” Savoie said. “That is the most accurate information for their size and model of canner.”

If you buy a used pressure canner or have lost the manual, then Savoie said you can likely find it online.

“The model number is always listed on the underside of the product,” Savoie said. “You can Google that. Oftentimes, you can find them for free online.”

From there, Savoie said to “do your homework.”

“There’s lots of great resources that are research based, tested and reliable, those are where I encourage people to go to get their correct information,” Savoie said. “There are risks [but] it’s a great way to take advantage of our local food supply when it’s in season.”

If you are interested in learning how to pressure can, Savoie said that the University of Maine Cooperative Extension will host online workshops and webinars throughout the month of August on how to do so.

Ultimately, despite the air of intimidation about it, pressure canning is just another type of canning that you can master if you want to.

“It really is just a different kind [of canning],” McCarty said. “It helps if you’re an experienced canner in terms of filling the jar and being comfortable with a canning recipe, but you could learn on either method. If you want to, you should just dive in.”