Almost nothing is better than a spoonful of freshly made blueberry jam spread over warm biscuits, scones or bread. Don't purchase ready-made jam when you can make some with flavorful fresh blueberries. When canned, your fresh jam will last for up to one year in the pantry. You can also make "freezer" jam, which doesn't require canning, although you'll have to refrigerate it and use it within a few weeks.
Preparing Your Blueberries
Use fresh or frozen blueberries to make the jam, and discard any moldy, bruised or soft berries. Wash the blueberries in a colander under cool, running water. Remove any stems or leaves from the berries. Once drained, place a layer of berries in a pot and crush them with a potato masher. Continue to add berries in layers and crush them all thoroughly. You can also place all of the berries in a food processor or blender and pulse them until they are as smooth or chunky as you like.
Making the Jam
Mix sugar, water, lemon juice and pectin into your smashed berries. Follow the package directions for your pectin to determine the amount you need. Use about a cup of sugar for each cup of mashed berries; the sugar helps the pectin to properly gel. Otherwise, the jam will turn out runny. The acid in the lemon juice also helps with the gelling process. Add 1/2 teaspoon of butter to prevent the jam from foaming during the cooking process. Cook the jam mixture over medium-high heat, while stirring it, until it reaches a full boil. Boil it for 1 minute.
Canning the Jam
Wash your canning jars and lids, and sterilize them by submerging them in boiling water for 10 minutes. Pour hot jam into the jars, leaving at least 1/4 inch of head space at the top of each jar. Use a boiling-water canner to process the jam jars. Wipe any excess jam from the rims of the jars and attach the lids and rings; place the jars into a canner or a large pot with enough water to submerge the jars. Once the water is boiling, cover the canner or pot; allow the jars to boil for 10 minutes. Remove the canner from the heat and let it sit for 5 minutes. Use jar tongs to remove the cans of jam; let them sit undisturbed for 24 hours.
Alternative Jam Making
If you don't want to make canned blueberry jam, make blueberry "freezer" jam instead. Simply combine your crushed blueberries with sugar; boil some water and pectin for a minute until it's blended and mix it into the berries. Place the jam into canning jars and allow it to set for 24 hours. Refrigerate the jars of jam at 40 degrees Fahrenheit or below, or freeze them at 0 F.
Storing the Jam
Reprocess any improperly sealed jars of canned jam or refrigerate them immediately. Properly sealed blueberry jam lasts for about a year in the pantry. Once opened, canned blueberry jam has the same shelf life as freezer jam -- about three weeks in the refrigerator or six months in the freezer. If your jam is moldy or smells unpleasant when you open it, discard it immediately.