Whether you’re a prepper, a saver, or a crunchy mamma (or all three), there’s a lot to like about eschewing the grocery store shelves in favor of your own preserved fruits and vegetables instead.
For guidance on canning, we spoke with Martha Zepp, the food preservation safety consultant for the Penn State Extension in Lancaster. The biggest mistake she sees people making is under-processing their canned foods.
“A sealed jar is not a safe jar,” she says, explaining that jars seal quickly but the water baths need to last much longer — till the food inside the jars reach a specific temperature, 240 degrees for tomatoes, for example, to kill the spores that can produce the deadly botulism toxin.
Below are the latest guidelines for water bath canning provided by the PennState Cooperative Extension.
Prepping the jars
Clean the jars first — wash in hot water with detergent and rinse well by hand, or wash in the dishwasher. If instructions call for jars to be sterilized, put in the pot, fill the pot, and then the jars, with hot water; bring to a boil and continue to boil for 10 minutes.
- Fill your canner pot halfway with water and heat to boiling.
- Load your filled, sealed jars into the canner rack and lower with handles, or load one jar at a time with a jar lifter onto the rack inside the canner.
- Add water, if needed, to 1-2 inches above jars; cover pot.
- When water returns to a vigorous boil, lower heat to maintain a gentle boil and process the jars for the time called for in the recipe.
- When processing is complete, turn off the heat and remove canner lid.
- Wait 5 minutes.
- Remove jars from the canner with a jar lifter and place on a towel or rack.
- Do not retighten the screw bands.
- Air-cool jars for 12 to 24 hours.
- Remove screw bands and check lid seals.
If lid is not sealed properly, throw out that lid and screw band and start the canning process for that jar again, from the first step (cleaning or sterilizing the jar).
You Say Tomato…
Tomatoes are delicious fresh from the garden, and canned and used in sauces months later. But because of their low acidity level, they carry a risk of botulism; botulism spores grow anaerobically—in the absence of air, making sealed jars perfect breeding grounds. As a safety precaution, you must increase the acidity level by always adding two tablespoons of bottled lemon juice (Zepp advises you not use a real lemon, due to inconsistent acidity levels) to the bottom of each quart jar before adding your tomatoes; if using pints, add one tablespoon of the lemon juice. You can substitute ½ teaspoon of citric acid crystals per quart for the lemon juice (or ¼ teaspoon for a pint container).
- Make sure that the tomatoes you’re planning to can are healthy. If there are signs of blight, or if they were picked from dead vines or vines exposed to frost, don’t use because of even lower acidity levels.
- Wash the tomatoes and dip in a boiling water bath for 30 to 60 seconds.
- Remove with a slotted spoon and plunge into cold water.
- Peel off the skins and remove the cores. Remove any bruised or discolored portions.
- For crushed tomatoes: Cut the tomato into quarters. Heat roughly 1/4 of the quarters in a large pot, crushing them with a wooden spoon. Stir frequently until boiling.
- Add the remaining tomato quarters, stirring constantly.
- Boil mixture for five minutes.
- Fill prepared canning jars (which have already had the lemon juice added; see note above) with hot crushed tomatoes, leaving 1/2-inch headspace.
- Remove any air bubbles by sliding a plastic knife or small rubber spatula between the tomatoes and the side of the glass jar. As the tomatoes settle, add more if necessary.
- Wipe rims of jars with a clean, dampened paper towel. Adjust lids and place in boiling water bath and process according to guidelines below.
Hot water bath times:
- Process crushed hot-pack tomatoes (above), or whole or half tomatoes packed in water, for 45 minutes. Even though the lids will seal sooner, this cooking time is necessary to kill off harmful organisms (yes, even though you’ve also used the lemon juice).
- Process whole or half tomatoes packed in a jar with added lemon but without added water for 85 minutes.
- NOTE: Do NOT add ingredients to your tomatoes (like onions, peppers, garlic, etc.) unless following a specific canning recipe as the ingredients can throw off the safe acidity level.
Fruits & jams
Fruits have a high acidity level, so canning them doesn’t carry the risk of botulism that tomatoes does. However, you do have to be aware of bacteria and mold growth; using a recipe that adds a lot of sugar to the fruit helps control this, as will the proper processing. When canning peaches and pears, after preparing the fruit (peeling, removing pit or core), follow a recipe for a light or medium syrup to use for canning the fruits.
Most jams and jellies call for pectin to be added; Zepp cautions that you follow the instructions on the pectin packet, as the directions for when and how you add powdered pectin differ from how you use liquid pectin, and if you substitute one for the other and introduce it in the incorrect way, you will get failed (runny) results.
Vegetables are low in acid, meaning a high risk for botulism when canning. We prefer not to stress about that and freezing them instead. It’s a simpler, safer and we think tastier, method, and you hold onto those nutrients. But blanch them first so they don’t continue to ripen and break down.
- Boil a gallon of water. Add a pound of vegetables. Cover. Return to a boil. Start timing.
- Blanch vegetables according to guidelines below. As soon as blanching is complete, strain vegetables and plunge into a few gallons of ice-cold water.
- After vegetables are cool, drain.
- If there is room in your freezer, spread vegetables out in single layer on waxed-paper covered cookie tray and place in freezer for several hours. When frozen, remove from tray and place vegetables in freezer storage bags, label, and return to freezer. This makes for clump-free freezing.
Note: You can also steam blanch your vegetables, ideal for broccoli and cauliflower, which will make them less soggy; if you go this route increase the blanching time by 50 percent.
Asparagus, small spears: 2 minutes; large spears: 4 minutes
Broccoli, 1½-inch pieces: 3 minutes
Carrots, sliced: 2 minutes
Cauliflower, small pieces: 3 minutes; large pieces: 5 minutes
Corn, whole cut kernel: 4 minutes
Green beans, small: 2 minutes; large: 3 minutes
Sugar peas, small: 2 minutes; large: 3 minutes
Zucchini or summer squash, ¼- to ½-inch slices: 3 minutes
Leslie Penkunas is the editor of Central Penn Parent.