Home food canning, preservation popular again. Here's how to do it.

Sometimes a watched pot does boil — and even steams.

The participants at the Johnston County, North Carolina, extension office stared at the pressure canner on the stove, steaming away. Its gauge read 12. That was high enough to preserve jars of fresh green beans if processed for 20 continuous minutes. But if the gauge dropped to 10, they’d have to start the clock over from zero.

“No pressure,” joked Katie Jernigan, 39.

They had gathered to learn how to can their own food from extension agent Gwen Williams. Though many pandemic sourdough starters have stopped, interest in canning — putting food in jars, then heat-sealing them — continues to seethe. All over: “I’ll have 25, 30 people every time I do a class,” Alabama extension canning guru Angela Treadaway said.

They don’t fit the stereotypes. Most of the Johnston students were in their 30s and 40s. Some were even male.

Here are the reasons the Johnston County participants gave:

The following information comes from Treadaway, Williams, the Department of Agriculture's canning guide and the National Center for Home Food Preservation.

Essentially, you’re doing several things to food that kill unsafe micro-organisms — most significantly heating it, but potentially also adding acid or sugar — and then vacuum-sealing it so nothing can enter or grow.

There are two canning methods.

In the water-bath method, you boil filled jars in a vat of water for a specific amount of time. This requires less specialized equipment but can be used only for foods that are 4.5 or lower on the pH scale.

The pressure-canning method works for a wider variety of food, including non-acidic vegetables (just about everything except rhubarb and most pickles), meats and soups. Because the jars are under pressure, their contents get hotter than 212 degrees Fahrenheit, killing more bacteria.

That’s it. Store the jars out of direct light. Eat sooner rather than later. Ball guarantees its Mason jar seals for 18 months, but “I don’t like them to have a birthday,” Williams said.

The USDA’s canning guide, the National Center for Home Food Preservation or state extension materials will tell you the method to use, the time to process, whether to pre-cook the contents and how much space to leave at the top of the jar. Some of these vary by altitude.

Consider taking a class through your local extension office, especially for the more complicated pressure method. Some offer webinars. Treadaway has had people sign up from literally around the world.

After the jars cool, test the seals. The lids should have sucked down and be flat or even a bit concave. You might hear them pop. If you can lift the lid off easily or if there is give in the lid, it didn’t work. You can either put the jar in the fridge and eat the contents right away, or process the product again, with a new lid and possibly a new jar, within 24 hours.

To start with, several big pots. Both canning methods take so much boiling water, you’d think you were in an old novel expecting a baby.

For water-bath canning, a proper canning pot and rack are handy, though you can also use a giant soup pot with something to keep jars off the bottom.

A pressure canner is a special device — don’t use an ordinary pressure cooker or an Instant Pot multicooker. Note that there is no such thing as a “USDA-approved” canner. The USDA sets standards for safe canning. It does not test or endorse specific brands or appliances, said Tracey Brigman, associate director for the National Center for Home Food Preservation.

You need new lids every time — the sealing rim works only once. You can reuse glass jars and rings.

Ball makes a utensil set with a wide-mouth funnel, jar-lifting tongs, a magnet stick to manipulate hot lids and a wand that tamps and measures produce in the jar. The Johnston County kitchen had multiple sets. Personally, speaking as a slapdash cheapskate, these utensils are worth it. Also useful: a ladle and silicone oven mitts/grippers.

Use high-quality produce. Cut off brown or shriveled bits. “Start off with a good product, and get it in the jar as soon as possible,” Treadaway said.

This problem was solved in the 1970s, when manufacturers added safety features. However, the jars inside can burst — especially if you try to cool down the canner quickly instead of letting it slowly lose pressure, release steam and return to room temp.

It “opens up our pores!” Williams said.

Don’t want to heat up your kitchen in the summer? Williams’ family used to can outside over a Coleman camping stove. Don’t use the big units meant for turkeys, she said. They’re too powerful.

Canning can be great, but it must be done safely. Yes, there are Facebook groups for rogue canners. But remember, mess around with a cake recipe and the worst you’ll get is a disappointment; mess around with canning, and you might get botulism. Botulism causes paralysis and sometimes death. You can’t taste it, smell it or wash it out. It is very bad. Both Treadaway and Williams mentioned the 2015 Ohio church potato salad outbreak that sickened at least 20 people and killed one.

So no matter what you see on social media, don’t can using an Instant Pot, your oven or your dishwasher’s sanitize cycle. Consult the USDA’s canning guide, the National Center for Home Food Preservation or a state extension source. You want a site that ends in .edu or .gov. Use their recipes for salsas and the like, not an old community cookbook.

Maybe you’re a pro at canning. Still, recommendations and practices change. Here are some that Treadaway highlighted.

Danielle Dreilinger is an American South storytelling reporter and the author of the book “The Secret History of Home Economics.” You can reach her at [email protected] or 919/236-3141.