You know how everyone on Instagram and Pinterest and various lifestyle blogs leads these neat-as-a-pin, picture-perfect lives surrounded by shelves of mason jars packed with jewel-like preserves that they presumably subsist on and they never die of botulism? This can be you—if you learn how to can safely. Not harming yourself or your loved ones with toxic bacteria from your homemade jam and jelly is incredibly easy, and just takes a few simple steps and pieces of equipment. I asked Ball’s still very much alive-and-well home-canning expert Jessica Piper for tips on canning preserves safely at home.
Get the right gear
Though it’s not strictly necessary to get special gear for canning, having the precise tool for the job makes tasks easier and safer. Ball’s starter kit (which I swear by) comes with a funnel that fits neatly into the mouth of almost any jar, a pair of pliers for lifting jars in and out of hot water, a magnetic wand to place the lids, a handy tool that both measures headspace (that’s the room between the filling and the lid) and removes bubbles from the liquid.
Here’s a fun fact: Jars are not all-purpose. If they’ve got straight sides, they’re freezer-safe, but if they have shoulders “like a person,” as Piper says, save them for pantry and fridge use. Glass jars are also not oven or microwave-safe, so ignore what you may have seen on the internet. Though jars and bands can be endlessly reused, it’s important to use a fresh lid every time because the seal—which is made of a proprietary porous material that expands and shrinks with pressure—degrades after the initial use. And don’t run them through the dishwasher like your grandmother did; that lady had some rusty lids.
Stick with the script
Recipes abound on the internet, and they might be madly delicious, but Piper cautions that they may or may not have been tested. Not for tastiness, or set, mind you—but for proper pH levels, cooking times, headspace, and other factors that influence the likelihood of bacterial infection. Ball tests and re-tests all of their recipes (like the Low-Sugar Strawberry-Tequila Agave Jam one below) with quality engineers in their Quality Assurance lab in Muncie, Indiana, which rigorously tests recipes for all of these factors. The National Center for Home Food Preservation uses those same standards as well. And even if you’re working with a recipe that’s been tested, resist the urge to make a double batch or use a larger jar. The amounts of acid and sugar, as well as the batch and yield size, have been specifically calculated so that everything is properly balanced and cooked through. If you like it that much, just take the time to craft a second round and have fun all over again.
And again, sorry grandma—even if you’ve been devoted to her apple butter recipe for decades, it’s important to do your research every year, either via your county extension office, the NCHFP, or Ball’s site freshpreserving.com. (Piper has worked there for years. She’s delightful and brings preserves to all her friends’ homes. She wants you to be well-fed and not perish and BTW, she's hosting plenty of Facebook Live events on July 22 for National Can-It-Forward Day.)
Pre-warming jars before filling them with hot jam, jelly or preserves reduces the possibility of their bottoms popping off from thermal shock. (Which is terribly shocking, says Piper—not to mention sticky as heck.) They also need time to cool down to room temperature after they’ve been processed in boiling water, and that’s got to happen organically or else the seal won’t seal properly and all your work will be for naught and you will be jelly-less, which is a pitiable state indeed.
Bide your time
It’s tempting to rush through the process and get right to the jam, because jam is magic, but patience is as much of an ingredient as fruit or pectin. The “assembly line” method of lining up jars and filling them may seem efficient, but Piper wisely points out that the last jar filled will be much cooler than the first, and variance is not what you’re looking for. Fill and seal each jar one by one, making sure to wipe the rim of the jar so nothing gets in the way of a tight seal. Once they’re all back in the pot, it’s time to process—which means waiting for a full boil and making sure that you’re letting it cook for as long as the (tested!) recipe recommends. Once the jars come out and you hear the sweet ping! of a lid popping, that doesn’t mean the jam is ready. Some take a full two weeks to set, and a lid may pop and un-pop several times before finally sealing while the pressure balances and it cools. It’s all part of the circle of life—and self-preservation.
Low-Sugar Strawberry-Tequila Agave Jam
Agave syrup is a low-glycemic sweetener derived from the agave plant, the same plant tequila is made from, so they naturally go together in this lightly sweetened strawberry jam.
Combine the first 2 ingredients in a 4-quart stainless steel or enameled Dutch oven. Crush berries with a potato masher.
Stir in pectin. Bring mixture to a full rolling boil that cannot be stirred down, over high heat, stirring constantly.
Stir in agave syrup. Return mixture to full rolling boil. Boil hard 1 minute, stirring constantly. Remove from heat. Skim foam, if necessary.
Ladle jam into a hot jar, leaving 1/4 inch headspace. Remove air bubbles. Wipe jar rim. Center lid on jar. Apply band, and adjust to fingertip tight. Place jar in boiling-water canner. Repeat until all jars are filled.
Process jars 10 minutes, adjusting for altitude. Turn off heat, remove pot lid, and let jars stand 5 minutes. Remove jars and cool.