Packed with berry flavor, this jam is tasty enough to eat off the spoon. Pectin is necessary to make a properly thickened jam, but rather than go for the store-bought kind we used apple peel for an all-natural spread.
Special equipment: We’re assuming that you already have basic tools lying around (like cutting boards, bowls, and measuring cups), so here’s the special equipment you’ll need for canning:
• Boiling water canner or 15- to 20-quart pot with a tightfitting lid
• Canning rack that fits inside the boiling water canner or 15- to 20-quart pot
What to buy: Bottled lemon juice may sound counterintuitive, but it helps ensure a uniform acidity level, which is vital to proper canning.
General canning tips: Before you turn on the heat, be sure to do the following: Read the recipe through, gather all necessary equipment, and check that you have the right amount of each ingredient on hand.
Give all your equipment a once-over: Examine your canning jars for nicks, cracks, uneven rims, or sharp edges that may prevent sealing or cause breakage; check that the lids have no dents and that the sealing compound is even and complete; and check that the bands fit properly.
Finally, have your jars, lids, and bands already sanitized before you start, and prepare only enough for one canner load at a time.
Blueberry jam – specific tips: Select fresh berries at their peak, and use firm, uniform-size produce free of any cracks, spots, or growths.
The jam is ready when it passes the plate test: Once you draw your finger through the cooled jam (see below), it should hold together on the plate without being runny. Don’t wait until it is a solid, unmovable mass or it will be overcooked and caramelized.
- 1Wash the jars, lids, and bands in hot, soapy water. Rinse well. Dry the lids and bands and set them aside.
- 2Place the jars in a boiling water canner or a 15- to 20-quart pot fitted with a canning rack and a lid. Fill the pot with water and bring it to a boil over medium-high heat. Boil for 10 minutes, then turn off the heat.
- 3Keep the jars in the hot water until you’re ready to use them.
For the jam:
- 1Place a plate in the freezer to chill for testing the jam. Place the blueberries in a large, heavy-bottomed saucepan and crush them with the back of a wooden spoon until some of the berries are broken up and they start to release their juice.
- 2Add the sugar and apple peel and stir to combine. Bring to a boil over medium-high heat. Boil vigorously, stirring frequently, until the jam reaches its setting point, about 15 minutes. (Bubbles will rise to the surface of the pan; if they get too high, just stir the jam until they decrease.)
- 3Once the jam reaches 228°F, start checking if it’s properly set. Conduct the plate test: Put a spoonful of jam on the chilled plate and place it in the freezer until the jam reaches room temperature, about 1 minute. Draw your finger through the jam. If it immediately runs back together, it’s not ready. Once the jam is ready, remove it from the heat and stir in the lemon juice.
- 4Remove the jars from the hot water with a jar lifter, letting any excess water drip off. Bring the water in the canner back to a simmer (about 180°F) for processing the packed jars. Fill the sterilized jars with jam, leaving a 1/4-inch headspace. (If you have a half-full jar, place it in the refrigerator and eat the jam within 5 days.)
- 5To remove any air bubbles, slide a clean rubber spatula down the side of each jar and press inward on the jam while rotating the jar; repeat 2 to 3 times for each jar.
For processing the packed jars:
- 1Wipe the rim and threads of each jar with a clean, damp towel. Place the lids on the jars, checking that the sealing compound is centered. Fit the jars with bands and tighten just until resistance is met.
- 2Check that the water in the pot or boiling water canner is at a simmer (about 180°F), then set the jars in the canning rack. (The jars must be covered by 1 to 2 inches of water. Add additional boiling water as necessary.)
- 3Cover the pot with a tightfitting lid and bring it to a rolling boil over medium-high heat. Process the jars for 10 minutes at a gentle but steady rolling boil. (Begin calculating the processing time once the water is at a rolling boil. Check occasionally that the water remains at a steady boil.)
- 4Once processed, remove the jars with the jar lifter and set them upright, 1 to 2 inches apart, on a dry towel. Do not retighten the bands; let the jars cool at least 12 hours.
- 5After the jars have cooled, check for a seal by pressing the center of each lid. If the center is concave and does not flex, remove the band and try to lift off the lid with your fingertips (don’t pull too hard). If you can’t lift the lid, there is a good vacuum seal. If the lid pops off, your jar did not properly seal. Eat the jam within 2 months.
- 6To store properly processed jars, wipe each lid and jar with a clean, damp cloth (the bands don’t need to stay on for storage), label the jars, and store them in a cool, dry, dark place. Unopened jars can be kept up to a year when stored properly. Once opened, keep in the refrigerator and use within 2 months.