This Balsamic Spiced Concord Grape Jam Recipe features sweet and aromatic Concord grapes, and is balanced with a touch of balsamic vinegar and accented with a hint of warm spices.
Slip the skins off the grapes and set aside for now.
Transfer the grape insides to a heavy-bottomed, lidded 5-quart pot. Cover the pot, bring to a simmer over medium heat, and simmer 10 minutes. Turn heat off and cool to room temperature (this will take up to a couple hours). Transfer the grape insides to a cheesecloth-lined sieve fitted over a bowl to catch the liquid; gently wring the cheesecloth to extract as much liquid as possible.
Transfer the grape liquid back to the pot along with the grape skins, sugar, lemon juice, balsamic vinegar, cinnamon, cloves, salt, and black pepper. Bring to a boil over high heat (uncovered), then turn heat down and simmer (uncovered) until jam is done (using one of the three tests), about 30 to 35 minutes, stirring frequently.
Transfer the jam to sterile jars; the jars should be preserved through canning or stored in the refrigerator.
This recipe makes about 5 ½ cups of jam, which is about 44 (2-tablespoon) servings.
Washing the Grapes: Wash the grapes before you de-stem them, but weigh them after (so you don't include the weight of the stems).
How to Tell When Jam is Done
There are three easy, reliable methods to help you determine when jam is done:
The Temperature Test: The jam should be at 220F (this is the magic number if you’re at sea level, like me). A cheapie candy thermometer works fine here.
The Sheet Test: Dip a wooden spoon into the jam and hold it sideways over the pot. The jam should fall off in a sheet, or the last jam to drip off should hang off the spoon in a bulging drop but not fall.
The Freezer Test: Freeze a plate, then put a little jam onto the frozen plate and put it back into the freezer for a few minutes. The jam should gel and not run.