CANNING BASICS
A SHORT HISTORY OF HOME CANNING
Whether you’re new to canning or an old hand at putting up, it’s comforting to know that people have been preserving food for millennia.
Long before there were glass jars to pack them in, there were pickled foods and potted jams. The term “canning” dates back to the military practice of putting food in tin canisters or “cans,” the method that kept Napoleon’s French soldiers fed in the early 1800s.
Glass jars weren’t widely used in the United States for home food preservation until after the Civil War. Early American cooks preserved foods mostly by smoking or drying them—or by putting them in crocks with salt, vinegar, sugar, or alcohol solutions; keeping them in the root cellar; periodically scraping off surface molds and scum; and taking their chances.
Self-sealing heatproof Mason jars, named for the fellow who invented them, were developed in the 1850s, and early attempts at canning in them yielded more than a few exploding jars, food poisonings, and deaths. It wasn’t until 1915 that scientists identified what was causing botulism poisoning, and the U.S. Department of Agriculture began developing guidelines to keep the anaerobic bacteria from canned goods. Modern canning practices—using heat, pressure, and acidity to kill or slow bacteria—stem from this.
Newer revelations about canning include:
• Those paraffin wax seals Grandma used on jams are a no-no. So is letting hot food cool in a hot jar to create a vacuum. Processing jars with canning lids in a covered pot of boiling water or a pressure canner for a specified length of time is essential.
• The acid or pH level of tomatoes and other foods can vary considerably depending on ripeness, freshness, variety, and growing conditions. Recipes that worked fine in the 1950s might not work as well with modern varieties and changing climates.
• Certain low-acid foods (meats, fish, most vegetables, ripe tomatoes, and some fruits) are most reliably and safely canned in a pressure canner. Alternatives include adding acid (vinegar or bottled lemon juice or citric acid powder) to the food before boiling-water canning—or preparing it for refrigerator or freezer storage rather than for the shelf.
• The density of the canned food (thin slices versus whole cucumbers) and the altitude where you’re canning (11 feet above sea level in Mobile, Alabama, or 13,000 feet in Denver, Colorado) affect sterilization and processing time. The thicker the food and the higher the altitude, the longer you’ll have to boil.
A LITTLE FOOD SCIENCE
There are three primary ways to halt or stop the growth of harmful bacteria that naturally occur in food: Heat or chill them to extremes, deprive them of oxygen and free water, and add enough acid to keep them from growing.
All three come into play in canning. To what degree and in what combination depend largely on how acidic the food is.
Acidity is measured in terms of pH. The higher the acidity, the lower the pH. On the scale (which ranges from 0 to 14, with 0 being the most acidic, 7 being neutral, and 14 being the most alkaline), 4.6 is the number to remember. It’s the bacterial breaking point.
Foods with a pH of 4.6 or lower (such as lemons and other citrus fruits) are considered high-acid foods. They contain enough acid to knock down bacteria that survive boiling and vacuum sealing in jars in a boiling-water canner.
Foods with a pH above 4.6 (meat, seafood, many vegetables, certain fruits) are low-acid foods. In these foods, botulism can grow at room temperature even after boiling and vacuum sealing.
To keep botulism from rearing up inside the jar, these foods must have enough acid (vinegar or lemon juice or citric acid) added to them to bring the pH below 4.6 or be heated under pressure in a pressure canner to temperatures not achieved by mere boiling. Alternately, they may be acidified and stored for shorter periods in the refrigerator or the freezer.
BOOK METHODOLOGY
Preserving in small batches helps ensure quality and allows you to can a little bit of a lot of things year-round. It means you don’t need an extra stove or a wheelbarrow full of produce to get started, and you likely won’t put up more than you’ll use in a year. That’s what we focus on in this book.
The recipes that follow generally require less than one full grocery bag of produce and one timed session in the canning pot. Each makes four to eight half-pints, three to five pints, or two to three quarts. The selection includes tried-and-true recipes from Southern Living that have been scaled down for smaller yields, pH tested, and updated to include best canning practices based on guidelines and recipes from the National Center for Home Food Preservation at The University of Georgia, jarmaker Ball, and university extension services.
Most of our recipes involve boiling-water canning to make them shelf-stable for up to a year. (We didn’t delve into pressure canning, which deserves its own book.) For safety, convenience, or the best flavor and texture, some recipes are designed for storage in the refrigerator or freezer rather than on the shelf.
“For the table” recipes included throughout provide unique ways to incorporate the items you’ve canned into your cooking. The yield with each recipe indicates how many and what size jars you’ll need as well as where the final product is headed—the shelf, the fridge, the freezer, or the table.
GETTING STARTED
CHOOSING & WASHING PRODUCE
For canning, always choose firm, ripe, recently harvested produce. Avoid blemished and overripe fruits and vegetables. Opt for organic when the peels will be used—as in marmalades and whole preserves.
Wash produce gently under cold running water, scrubbing only if needed to remove waxy coatings. Trim roots, stems, and any blemished or bruised spots.
CHOOSING & WASHING JARS
Because canning jars of the same volume come in multiple shapes (slender half-pints can look almost as big as standard pints), it can be easy to confuse sizes. But jar size is critical to recipe success and safety. Look for markings on the bottom and sides of the jars, and use a measuring cup and water if you’re not sure. Four-ounce jars hold a half cup. Half-pints hold one cup. Pints hold two cups. Quarts hold four cups. Standard and widemouthed jars can be used interchangeably, as long as they have the same volume. Widemouthed jars need widemouthed lids and bands.
Whether your jars are new or old, inspect them carefully. Discard any with chips, bubbles, and cracks, as they may break in the canner. Use bands that are free of rust. If your jars have mineral or hard water deposits from previous canning, soak them overnight in a vinegar solution (one cup vinegar for each gallon of water) to remove the cloudy film. Wash jars and bands in the dishwasher or in a basin of hot soapy water. Rinse thoroughly, and let air dry. Always use new lids.
GATHERING UP THE GEAR
Beyond the jars, bands, and lids, the basic canning gear may already be in your kitchen.
If you don’t have a canning pot with a rack, you can use a large stockpot or Dutch oven with a lid, as long as the pot is wide enough to hold the number of jars called for in the recipe and three inches deeper than your rack and jars.
If you don’t have a canning rack, you can use a round trivet or cooling rack that fits in the pot, or even a folded towel on top of a few jar bands, to keep jars off the bottom. This minimizes risk of jar breakage and allows boiling water to flow all around the jars.
Though a jar lifter with curved sides and rubberized grips is ideal for handling hot jars, regular tongs or a waterproof silicone oven mitt can be used in a pinch. And, while a candy thermometer is helpful for testing the readiness of jams and jellies, you can also figure it out with a cold saucer or a spoon.
BASIC GEAR
1. CANNING POT large enough to hold rack, jars, and water to cover by 2 inches, and A RACK that holds jars off bottom
2. RUBBER-COATED JAR LIFTER to maneuver jars in and out of the pot
3. TONGS or lid wand to transfer lids from hot water to jars
4. STONEWARE BAKING DISH or heatproof bowl for warming lids
5. WIDEMOUTHED FUNNEL to keep jar rims clean
6. KITCHEN TIMER to time the boil
7. NONREACTIVE SAUCEPAN (enameled or stainless steel-clad metal, not aluminum), MEASURING CUP (glass is nice), and UTENSILS (wood or stainless steel spoon, ladle, and slotted spoon/skimmer) to avoid chemical reactions with brines and other acidic mixtures that can cause a metallic taste
8. NEW CANNING LIDS, the flat metal discs with the rubbery ring seal on one side
9. NEW OR USED GLASS JARS specifically designed for canning, such as Ball- or Kerr-brand Mason jars, as long as they are free of chips, bubbles, or cracks
10. NEW OR USED BANDS, the screw-top rings that secure the lids until they are sealed
11. CHOPSTICK or other small plastic, ceramic, or wooden tool to remove air bubbles
12. CLEAN TOWELS OR WOODEN CUTTING BOARD on which to rest the hot jars and paper towels to wipe rims
INGREDIENTS NOT TO FUDGE
• Vinegar: Use vinegars labeled 5% acidity.
• Lemon juice: Bottled lemon juice has a more constant acidity than fresh lemon juice. In recipes that rely on lemon juice not just for flavor but for the proper acidity, such as those involving ripe tomatoes, we specify—and you should use—bottled lemon juice for safety.
• Water for pickling brines: Use soft or distilled water because minerals in hard water can cause discoloration (think: safe but unsightly blue garlic) and also unsafely lower the pH of pickled low-acid foods. (For instructions on softening hard water.)
• Canning-and-pickling salt: Do not substitute kosher, sea, table, or other salts, which have different volumes and may contain additives that cloud brines.
• Sugar: Don’t futz with the amount. If you decrease it in jam and jelly recipes, it may alter the sugar’s ability to keep the food preserved once it’s opened as well as reduce your odds of getting that jelly to set.
• Pectin: Some fruit preserves rely on the pectin naturally occurring in the fruit or its peels or seeds for thickening; others use a precanning fermentation or long cooking. If the recipe uses added pectin, be sure to use the type and amount specified. Powdered generally sets up firmer than liquid and thus is often preferred for jellies and marmalades. Liquid is often better suited to softer jams and looser preserves. And some are specifically designed for freezer preserves (sometimes labeled freezer, sometimes labeled instant).
METHODS NOT TO FUDGE
• Boil times for sterilizing and processing: These are key to safety. Set your timer only after the water has come or returned to a boil.
• Warming method for lids: The flexible compound that forms the seal needs only to be warmed in hot water to soften. Boiling lids before they go onto the jars can damage the seal. Also, be sure they’re not clumped together in the warming bowl or pot. You want each one to get adequately softened but not to stick to its neighbor.
• Jar size and headspace: Processing times are based on the density of the food and the volume in the jar. If a jar is underfilled, not all of the air will be forced out during the process, and you won’t get a good seal. If it’s overfilled, the food can bubble out during processing and get stuck between the lid and the jar; there again, you won’t get a good seal. And if you use the wrong-size jar, you may not be processing long enough.
• Timing of steps so hot food goes into hot jars: Jars need to be sterilized while you’re finishing up the food that’s going in them so that everything’s hot when they meet. If your food prep ends up taking longer, just keep the jars in the pot at a low simmer until you’re ready.
• Transfering full jars: Don’t tip filled jars as you put them in or remove them from the water bath, which can sully the rim and interfere with the seal.
• Checking the seals: Always remove the bands and check lid seals 12 to 24 hours after canning. If jars aren’t sealed, they’re not safe to store on the shelf.
GENERAL INSTRUCTIONS FOR BOILING-WATER CANNING
STERILIZE JARS & PREPARE LIDS
Place clean canning jars on a rack in the bottom of the canning pot, and add water to fill the jars and cover them by two inches (1). Cover the pot, and bring the water to a rolling boil over high heat.
After the water reaches a boil, boil for 10 minutes, adjusting time as needed for your altitude*; then reduce the heat, and maintain at a simmer until you’re ready to fill the jars. Jars must be hot when food or hot mixtures go into them.
Place the lids in a stoneware baking dish or heatproof bowl. Fan them out to ensure they’re not clumped together.
FILL & PROCESS JARS
Remove jars from the simmering water using a jar lifter, and carefully pour the water in the jars back into the pot. Place the jars upright on a clean towel or large wooden cutting board. Ladle enough simmering water over the lids to cover them (2). This warms the gasket on the underside of the lid and helps them seal. Cover the pot, and maintain at a simmer.
Pack any recipe-specified solid ingredients (such as herbs or cut vegetables for a pickle) into the hot jars. Ladle or pour hot mixture or brine into the hot jars, using a widemouthed funnel to help keep the jar rims clean (3). Leave the recipe-specified amount of headspace, the space from the very top of the jar to the surface of the liquid or food inside (4). Repeat with remaining jars, working quickly to ensure that hot mixtures go into hot jars.
Tap the jars lightly to help the contents settle, and stir gently with a chopstick or thin plastic or wooden utensil to free any trapped air bubbles (5). Add more hot mixture or brine as needed to reach the correct headspace. Wipe the rims clean of any spilled food using a paper towel dipped in hot water.
Pour the water from the stoneware dish with the lids into the canning pot, and use tongs or a magnetic lid wand to quickly place a lid, white side down, on top of each jar.
Place a band onto each jar; screw just until fingertip-tight (6). Do not overtighten.
Carefully lower the filled jars into the pot of simmering water using the jar lifter to keep them upright (7). Tipping can cause food to get between the jar and the lid and interfere with the seal. Add more water if needed to bring the water level to two inches above the jar tops.
Cover the pot, increase the heat, and return the water to a full rolling boil. After the water reaches a boil, set a timer, and boil for the amount of time specified in the recipe, adjusting if needed for your altitude (8).*
Turn off the heat, uncover the pot, and wait until the boiling has subsided (about 5 minutes). Remove jars using the jar lifter, being careful to keep them upright (7).
Transfer jars to a towel-lined or wooden surface where they can rest undisturbed 12 to 24 hours (9). Do not tighten or adjust bands. Lids may make a popping noise as the jars cool. Not to worry. That’s one sign of an airtight seal—and the sound of canning success.
CHECK SEALS, LABEL & STORE
When the jars have cooled 12 to 24 hours, remove the bands and inspect the lids. Each lid should be sucked down a little in the middle and firmly attached at the edges. Press down on the center of each lid with your finger (10). If the lid doesn’t move, the jar is sealed and can be stored in a cool, dark place for up to 1 year (or as specified in the recipe).
If the lid center depresses and pops up again, the jar isn’t sealed and should be refrigerated immediately and its contents used within a few days. (You can reheat the contents of an improperly sealed jar, pack in a freshly sterilized hot jar, and process again, though this can alter the desired texture and flavor.)
Label and store properly sealed jars without the bands (11). This allows you to better spot oozing, surface mold, rusting, and other signs of spoilage around the lid and frees up the bands for another canning batch. Refrigerate jars after opening.
WHAT TO DO WITH PARTIAL JARS
Depending on how fast you simmered, how much you skimmed off when removing foam, how much you tasted along the way, and the quality of your produce, you may have a few tablespoons more or less than you need for the proper headspace. Tempting though it may be, don’t overfill the jars, and don’t process jars that are only partially full (12). Headspace is critical to achieving an airtight seal and proper processing. Too little headspace and your mixture may boil over during processing and get between the lid and the jar. Too much and it may overcook and never force out enough air to produce a vacuum seal. Instead, enjoy any partial jars immediately, or refrigerate and use within a week.
* If you’re canning at altitudes above 1,000 feet above sea level, you must adjust boiling times. If you’re at 1,001 to 6,000 feet above sea level, add 5 minutes boiling time. If you’re at altitudes of 6,001 feet or higher, add 10 minutes boiling time. You can find approximate elevations of land features in your area with the U.S. Geological Survey online tool (http://geonames.usgs.gov/pls/gnispublic). For the most accurate altitudes, check with your local government, planning commission, or cooperative extension service.
GEL TESTS FOR JAMS, JELLIES & PRESERVES
Use these tests to check for thickening when your fruit mixture begins to sputter more than foam, and the surface takes on a glossy sheen.
TEMP TEST
Use a candy thermometer while the mixture boils or simmers. Remove from the heat when the mixture registers 220°, the temperature at which fruit-sugar mixtures gel.
FREEZER TEST
Put a few saucers in the freezer to chill before you cook the fruit mixture. When it appears to have thickened or hits the cook time specified in the recipe, spoon a small amount onto a chilled saucer. Wait a few seconds then push a trail through it with your finger. Does it wrinkle at the edge, form a slight skin, and hold the trail? It’s likely set. Does it part briefly and then run back together like honey? Cook it a bit more, and repeat the test.
DRIP TEST
Run a spoon through the jelly or jam, and turn the spoon on its side, letting the mixture run off the spoon. Does it drip rapidly in individual drops? It’s not set. Do the last drops combine and lazily fall in a sheet from the back of the spoon? It’s likely set.
HELPFUL HINTS FROM THE TEST KITCHEN
Start with hot water in the canning pot to reduce the time it takes to come to a boil.
If you don’t have soft water and are using hard water to sterilize and process jars, add ¼ cup vinegar for each gallon of water in the canning pot to avoid leaving cloudy mineral deposits on the jars.
Always use new canning lids purchased within the past year. Even if the package is unopened and the lids are unused, the seals can degrade over time.
Save the boxes that canning jars are sold in; they come in handy when transporting canned products and storing the emptied jars for reuse.
Use a Microplane to zest citrus. It produces tiny strands that are uniform in the final product and avoids pith that can turn canned goods bitter or cloudy.
If the spices and herbs you’re using aren’t going in the finished jar, put them in cheesecloth tied with kitchen string to make them easier to fish out. You don’t want to be hunting for a rosemary sprig in a pot of scalding hot jam.
Use the size of saucepan or Dutch oven specified in the recipe, even if it seems larger at first than you think you need. Larger pans help avoid boilover.
A small stoneware baking dish is ideal for warming lids. It holds heat nicely, is wide enough to let you scatter the lids and keep them from sticking together, and is shallow enough to make fishing out the lids easy.
Don’t stir jam or jelly mixtures with whisks. That can introduce air bubbles you don’t want in the finished product. Use a wooden or nonaluminum spoon.
Jam- and jelly-making can be sticky business. You’ll be stirring often. Have a clean spoon rest handy to minimize sticky stove-tops and counters and avoid introducing counter bacteria into your fruit mixture.
Always let boiled mixtures stand off the heat at least one minute before skimming. This allows the foam to rise and the food to settle, making skimming easier.
Stir mixtures after skimming and before and between ladling into jars to ensure each jar gets an equal amount of mixed solids or liquid and solids.
Fill jars on wax paper-lined jelly-roll pans to catch drips and make moving the jars from your workspace to the stove easier.
Many preserves with added spices and herbs—and most canned pickles—taste best and achieve their best texture after three weeks in the jar.
Having doubts about your jelly setting after you’ve canned it? Look at what’s left in the pot. Does it cling to the sides? It’s likely set. If your jelly or jam seems too thin when you check the seals, don’t fret. Some jellies take a week or more to fully set. If yours doesn’t after two weeks, call it syrup, and store it in the fridge. It’ll still taste great.
Using soft or distilled water (as opposed to hard water) when canning helps prevent unintended chemical reactions between minerals in the water and items in the jar.
If you have hard water (you’ll know if it leaves rust or calcium deposits on your faucets and fixtures), you can soften it by boiling it for 15 minutes, letting it stand 24 hours, and pouring off carefully to leave settled sediment at the bottom.
Screw-top freezer-safe plastic containers are good options for freezer preserves.
If you freeze preserves in glass jars, be sure to thaw the frozen jars one day in the fridge before using. Don’t run a frozen jar under hot water or put it in the microwave. Frozen glass jars may crack with a severe temperature change.
Though pretty, antique jars and used one-piece lids are not safe for boiling-water canners. Save them for refrigerator versions and items you keep in the fridge or bring to the table.
Always use a new lid, a rust-free band, and a jar free of chips, cracks, and bubbles that is specifically made for canning if you’re going to put it in the canning pot.
SPOILAGE SIGNS TO WATCH FOR
• Foaming or fizzing in the jar after it’s been sealed
• Rancid, sour, or yeasty odors when you open the jar
• Food bubbling in or exploding from a sealed jar
• Lids that bulge or loosen after initial sealing
• Powder, mold, or film on the surface of the food
NOT IDEAL, BUT USUALLY NOT A BIG DEAL
• Cloudiness in the jar if you’ve used ground spices or table salt in the recipe. Those ingredients can cloud a brine.
• Film on the outside of the jar. Most often this is just a hard water or mineral deposit from the water in your canner.
• Black specks on the bottom of the lids of canned tomatoes. It’s a natural reaction and doesn’t alone signal spoilage.
• Blue garlic at the bottom of your pickles. If garlic’s very young, not fully dried out, or not completely cooked, a component in it may react with copper in your cookware or minerals in your water, making it turn blue. It’s unsightly but not harmful.
• Fruit float. If the fruit pieces in your preserves float to the top of the jar rather than being suspended evenly throughout, it’s OK. That jar probably won’t win you a blue ribbon at the fair, but it’ll still be delicious. Just give the contents a stir when you open the jar.
• When in doubt, throw it out!