Blueberry-lemon jam recipe

4 1/2 c Blueberries; fresh or frozen
7 c Sugar
2 tb Lemon juice
Grated zest of 2 large lemon
3 3-oz pouches liquid pectin
Pick over the fresh blueberries to remove any stalks and rinse under cold water. Drain well and place in a large heavy-bottomed saucepan. (Do not rinse or thaw the frozen berries.) Crush the berries slightly with a potato masher or pestle. Stir in the sugar, lemon juice, and zest. Bring to a boil over medium-high heat, stirring often. When the mixture reaches a full boil, cook for 1 minute. Stir in the pectin. Return to a full boil, then cook for another minute. Ladle into hot, sterilized jars leaving 1/4 inch of headroom. Wipe the rims clean and put the lids on top of the jars. Process in a boiling water bath for about 5 minutes. Remove from the water and cool completely at room temperature.
Makes about 6 cups.